diff --git a/src/main/java/gov/nasa/pds/tools/util/FlagsUtil.java b/src/main/java/gov/nasa/pds/tools/util/FlagsUtil.java
index cda41a4a8..facfa0da9 100644
--- a/src/main/java/gov/nasa/pds/tools/util/FlagsUtil.java
+++ b/src/main/java/gov/nasa/pds/tools/util/FlagsUtil.java
@@ -38,6 +38,9 @@ public class FlagsUtil {
   /** Flag to enable/disable stack trace printing. */
   private static boolean stackPrintingFlag = false;
 
+  /** Flag to downgrade member_not_found from ERROR to WARNING (for accumulating bundles). */
+  private static boolean skipStrictCollectionMembership = false;
+
   /**
    * Initialize flags to their default states
    *
@@ -48,6 +51,7 @@ public static void initialize() {
     FlagsUtil.contentValidationFlag = true;
     FlagsUtil.skipProductValidation = false;
     FlagsUtil.stackPrintingFlag = false;
+    FlagsUtil.skipStrictCollectionMembership = false;
     LOG.debug("initialize:contentValidationFlag {}", FlagsUtil.contentValidationFlag);
     LOG.debug("initialize:skipProductValidation {}", FlagsUtil.skipProductValidation);
   }
@@ -115,6 +119,15 @@ public static boolean getSkipProductValidation() {
     return (FlagsUtil.skipProductValidation);
   }
 
+  public static void setSkipStrictCollectionMembership(boolean flag) {
+    FlagsUtil.skipStrictCollectionMembership = flag;
+    LOG.debug("setSkipStrictCollectionMembership: {}", FlagsUtil.skipStrictCollectionMembership);
+  }
+
+  public static boolean getSkipStrictCollectionMembership() {
+    return FlagsUtil.skipStrictCollectionMembership;
+  }
+
   /**
    * Set the severity value
    *
diff --git a/src/main/java/gov/nasa/pds/tools/validate/ProblemType.java b/src/main/java/gov/nasa/pds/tools/validate/ProblemType.java
index ae61c51c5..4155f961d 100644
--- a/src/main/java/gov/nasa/pds/tools/validate/ProblemType.java
+++ b/src/main/java/gov/nasa/pds/tools/validate/ProblemType.java
@@ -211,6 +211,8 @@ public enum ProblemType {
 
   MEMBER_NOT_FOUND("warning.integrity.member_not_found"),
 
+  MEMBER_NOT_FOUND_ERROR("error.integrity.member_not_found"),
+
   INTEGRITY_PDS4_VERSION_MISMATCH("warning.integrity.pds4_version_mismatch",
       ProblemCategory.GENERAL),
 
diff --git a/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/BundleReferentialIntegrityRule.java b/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/BundleReferentialIntegrityRule.java
index 90dc8da45..1f9ec6c54 100644
--- a/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/BundleReferentialIntegrityRule.java
+++ b/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/BundleReferentialIntegrityRule.java
@@ -25,6 +25,7 @@
 import gov.nasa.pds.tools.util.EveryNCounter;
 import gov.nasa.pds.tools.util.ReferentialIntegrityUtil;
 import gov.nasa.pds.tools.util.Utility;
+import gov.nasa.pds.tools.util.FlagsUtil;
 import gov.nasa.pds.tools.util.XMLExtractor;
 import gov.nasa.pds.tools.validate.Identifier;
 import gov.nasa.pds.tools.validate.ProblemDefinition;
@@ -172,9 +173,12 @@ private void getBundleMembers(URL bundle) {
         }
         if (matchingMembers.isEmpty() && "Primary".equalsIgnoreCase(memberStatus)) {
           LOG.debug("getBundleMembers:MATCHING_MEMBER_ID_IS_EMPTY {}", id);
+          boolean downgradeToWarning = FlagsUtil.getSkipStrictCollectionMembership();
           getListener()
-              .addProblem(new ValidationProblem(new ProblemDefinition(ExceptionType.WARNING,
-                  ProblemType.MEMBER_NOT_FOUND, "The member '" + id + "' could not be found in "
+              .addProblem(new ValidationProblem(new ProblemDefinition(
+                  downgradeToWarning ? ExceptionType.WARNING : ExceptionType.ERROR,
+                  downgradeToWarning ? ProblemType.MEMBER_NOT_FOUND : ProblemType.MEMBER_NOT_FOUND_ERROR,
+                  "The member '" + id + "' could not be found in "
                       + "any product within the given target."),
                   bundle));
         } else if (matchingMembers.size() == 1) {
diff --git a/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/CollectionReferentialIntegrityRule.java b/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/CollectionReferentialIntegrityRule.java
index d97c79bf7..00572e4e7 100644
--- a/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/CollectionReferentialIntegrityRule.java
+++ b/src/main/java/gov/nasa/pds/tools/validate/rule/pds4/CollectionReferentialIntegrityRule.java
@@ -27,6 +27,7 @@
 import gov.nasa.pds.tools.inventory.reader.InventoryReaderException;
 import gov.nasa.pds.tools.inventory.reader.InventoryTableReader;
 import gov.nasa.pds.tools.label.ExceptionType;
+import gov.nasa.pds.tools.util.FlagsUtil;
 import gov.nasa.pds.tools.util.ReferentialIntegrityUtil;
 import gov.nasa.pds.tools.util.Utility;
 import gov.nasa.pds.tools.util.XMLExtractor;
@@ -205,11 +206,14 @@ private void validateEntry(URL collection, int numOfCollectionMembers, Inventory
           "getCollectionMembers: id,matchingMembers.isEmpty(),entry.getMemberStatus() {},{},{}",
           id, matchingMembers.isEmpty(), entry.getMemberStatus());
       if (matchingMembers.isEmpty() && "P".equalsIgnoreCase(entry.getMemberStatus())) {
+        boolean downgradeToWarning = FlagsUtil.getSkipStrictCollectionMembership();
         getListener()
-            .addProblem(new ValidationProblem(new ProblemDefinition(ExceptionType.WARNING,
-                ProblemType.MEMBER_NOT_FOUND, "The member '" + id + "' could not be found in "
+            .addProblem(new ValidationProblem(new ProblemDefinition(
+                downgradeToWarning ? ExceptionType.WARNING : ExceptionType.ERROR,
+                downgradeToWarning ? ProblemType.MEMBER_NOT_FOUND : ProblemType.MEMBER_NOT_FOUND_ERROR,
+                "The member '" + id + "' could not be found in "
                     + "any product within the given target."),
-                    collection));
+                collection));
       } else if (matchingMembers.size() == 1) {
         super.verifyLidPrefix(id.getLid(), this.lid, entry.getMemberStatus(), collection);
         getListener()
diff --git a/src/main/java/gov/nasa/pds/validate/ValidateLauncher.java b/src/main/java/gov/nasa/pds/validate/ValidateLauncher.java
index 0122f46dc..30c3034fa 100644
--- a/src/main/java/gov/nasa/pds/validate/ValidateLauncher.java
+++ b/src/main/java/gov/nasa/pds/validate/ValidateLauncher.java
@@ -237,6 +237,8 @@ public class ValidateLauncher {
 
   private boolean allowUnlabeledFiles;
 
+  private boolean skipStrictCollectionMembership;
+
   private File registeredProductsFile;
 
   private File nonRegisteredProductsFile;
@@ -288,6 +290,7 @@ public ValidateLauncher() throws TransformerConfigurationException {
     contextMismatchAsWarn = true;
     spotCheckData = -1;
     allowUnlabeledFiles = false;
+    skipStrictCollectionMembership = false;
     registeredAndNonRegistedProducts = new HashMap<>();
     registeredProductsFile = new File(
         System.getProperty("resources.home") + File.separator + ToolInfo.getOutputFileName());
@@ -477,6 +480,9 @@ public void query(CommandLine line) throws Exception {
         setSpotCheckData(value);
       } else if (Flag.ALLOW_UNLABELED_FILES.getLongName().equals(o.getLongOpt())) {
         setAllowUnlabeledFiles(true);
+      } else if (Flag.SKIP_STRICT_COLLECTION_MEMBERSHIP.getLongName().equals(o.getLongOpt())) {
+        setSkipStrictCollectionMembership(true);
+        FlagsUtil.setSkipStrictCollectionMembership(true);
       } else if (Flag.LATEST_JSON_FILE.getLongName().equals(o.getLongOpt())) {
         setUpdateRegisteredProducts(true);
       } else if (Flag.NONREGPROD_JSON_FILE.getLongName().equals(o.getLongOpt())) {
@@ -852,6 +858,10 @@ public void query(File configuration) throws ConfigurationException {
       if (config.containsKey(ConfigKey.ALLOW_UNLABELED_FILES)) {
         setAllowUnlabeledFiles(true);
       }
+      if (config.containsKey(ConfigKey.SKIP_STRICT_COLLECTION_MEMBERSHIP)) {
+        setSkipStrictCollectionMembership(true);
+        FlagsUtil.setSkipStrictCollectionMembership(true);
+      }
       if (config.containsKey(ConfigKey.LATEST_JSON_FILE)) {
         setUpdateRegisteredProducts(true);
       }
@@ -1160,6 +1170,10 @@ public void setAllowUnlabeledFiles(boolean flag) {
     this.allowUnlabeledFiles = flag;
   }
 
+  public void setSkipStrictCollectionMembership(boolean flag) {
+    this.skipStrictCollectionMembership = flag;
+  }
+
   private void setRegisteredProducts() {
     URL url = null;
 
@@ -1396,6 +1410,8 @@ public void setupReport(String cliArgs[]) throws IOException {
         || validationRule.equalsIgnoreCase("pds4.collection"))) {
       report.addParameter("allowUnlabeledFiles", "Allow Unlabeled Files",
           String.valueOf(allowUnlabeledFiles));
+      report.addParameter("skipStrictCollectionMembership", "Allow Unlisted Members",
+          String.valueOf(skipStrictCollectionMembership));
     }
     report.addParameter("maxErrors", "Max Errors", String.valueOf(maxErrors));
     report.addParameter("registeredContextsFile", "Registered Contexts File",
diff --git a/src/main/java/gov/nasa/pds/validate/commandline/options/ConfigKey.java b/src/main/java/gov/nasa/pds/validate/commandline/options/ConfigKey.java
index 6f8c9182e..a9a6d2be2 100644
--- a/src/main/java/gov/nasa/pds/validate/commandline/options/ConfigKey.java
+++ b/src/main/java/gov/nasa/pds/validate/commandline/options/ConfigKey.java
@@ -147,6 +147,11 @@ public class ConfigKey {
    */
   public static final String ALLOW_UNLABELED_FILES = "validate.allowUnlabeledFiles";
 
+  /**
+   * Property to downgrade member_not_found from ERROR to WARNING (for accumulating bundles).
+   */
+  public static final String SKIP_STRICT_COLLECTION_MEMBERSHIP = "validate.skipStrictCollectionMembership";
+
   /**
    * Property to download the latest Registered Context Products JSON file and replace the existing
    * file.
diff --git a/src/main/java/gov/nasa/pds/validate/commandline/options/Flag.java b/src/main/java/gov/nasa/pds/validate/commandline/options/Flag.java
index fa4d8dc01..59351c1be 100644
--- a/src/main/java/gov/nasa/pds/validate/commandline/options/Flag.java
+++ b/src/main/java/gov/nasa/pds/validate/commandline/options/Flag.java
@@ -171,6 +171,10 @@ public enum Flag {
   ALLOW_UNLABELED_FILES(null, "allow-unlabeled-files",
       "Tells the tool to not check for unlabeled files in a bundle or collection."),
 
+  SKIP_STRICT_COLLECTION_MEMBERSHIP(null, "skip-strict-collection-membership",
+      "When set, collection inventory members not found in the target are reported as warnings instead of errors. "
+          + "Use when validating partial or accumulating bundles where prior-release products are intentionally absent."),
+
   RULE("R", "rule", "validation rule name", String.class,
       "Specifies the validation rules to apply. (pds4.bundle|pds4.collection|pds4.folder|pds4.label|pds3.volume)."
           + " Default is pds4.label"),
diff --git a/src/main/java/gov/nasa/pds/validate/commandline/options/FlagOptions.java b/src/main/java/gov/nasa/pds/validate/commandline/options/FlagOptions.java
index 90752db32..1a914573c 100644
--- a/src/main/java/gov/nasa/pds/validate/commandline/options/FlagOptions.java
+++ b/src/main/java/gov/nasa/pds/validate/commandline/options/FlagOptions.java
@@ -74,6 +74,7 @@ public class FlagOptions {
     options.addOption(new ToolsOption(Flag.NO_DATA));
     options.addOption(new ToolsOption(Flag.SPOT_CHECK_DATA));
     options.addOption(new ToolsOption(Flag.ALLOW_UNLABELED_FILES));
+    options.addOption(new ToolsOption(Flag.SKIP_STRICT_COLLECTION_MEMBERSHIP));
     options.addOption(new ToolsOption(Flag.LATEST_JSON_FILE));
     options.addOption(new ToolsOption(Flag.NONREGPROD_JSON_FILE));
     options.addOption(new ToolsOption(Flag.SKIP_CONTEXT_VALIDATION));
diff --git a/src/site/markdown/operate/index.md b/src/site/markdown/operate/index.md
index 934a309ec..8bb368a29 100644
--- a/src/site/markdown/operate/index.md
+++ b/src/site/markdown/operate/index.md
@@ -451,6 +451,18 @@ and is in line with the other bundle data.
 % validate --skip-product-validation --rule pds4.bundle --target path/to/staged/bundle_v2 --alternate_file_paths path/to/online/bundle_v1
 ```
 
+#### Validating Partial/Incremental Bundle Deliveries
+
+By default, validate reports an **error** (`error.integrity.member_not_found`) when a collection inventory lists a primary member product that cannot be found in the validation target. This is the correct behavior for complete bundles.
+
+When validating a partial or incremental delivery of an accumulating bundle — where prior-release products are intentionally absent from the local target — use the `--skip-strict-collection-membership` flag to downgrade this condition to a warning:
+
+```
+% validate --skip-strict-collection-membership --rule pds4.bundle --target path/to/incremental/bundle
+```
+
+This flag should only be used when you have a legitimate reason for missing members (e.g., products delivered in a previous release). For standard bundle validation, the default error behavior is correct and should not be suppressed.
+
 #### Example of using multiple-flags to improve performance
 
 Here is one example of how to
diff --git a/src/test/resources/features/4.2.x.feature b/src/test/resources/features/4.2.x.feature
new file mode 100644
index 000000000..a2303f1e8
--- /dev/null
+++ b/src/test/resources/features/4.2.x.feature
@@ -0,0 +1,15 @@
+Feature: 4.2.x
+  Scenario Outline: NASA-PDS/validate#<issueNumber>-<subtest>
+    Given validate issue <issueNumber>, test <subtest>, and test data at <datasrc>
+    When execute validate with <args>
+    Then compare to the expected outcome <expectation>.
+    @4.2.x
+    Examples:
+      | issueNumber | subtest | datasrc | args | expectation |
+#begin
+
+# github1601: member_not_found should be ERROR by default; --skip-strict-collection-membership downgrades to WARNING
+| 1601 | 1 | "github1601" | "-R pds4.bundle --skip-context-validation -t {datasrc}/bundle_test_1601.xml" | "summary:totalErrors=1,summary:referentialIntegrity:failed=1,summary:messageTypes:error.integrity.member_not_found=1" |
+| 1601 | 2 | "github1601" | "-R pds4.bundle --skip-context-validation --skip-strict-collection-membership -t {datasrc}/bundle_test_1601.xml" | "summary:totalWarnings=1,summary:messageTypes:warning.integrity.member_not_found=1" |
+
+#end
diff --git a/src/test/resources/features/pre.3.6.x.feature b/src/test/resources/features/pre.3.6.x.feature
index 6f248581a..8bd617330 100644
--- a/src/test/resources/features/pre.3.6.x.feature
+++ b/src/test/resources/features/pre.3.6.x.feature
@@ -80,8 +80,8 @@ Feature: < 3.6
 | 416 | 2 | "github416" | "-R pds4.label -t {datasrc}/mix_raw_calib_mixs-c_sw_offset_table_20160301_invalid.xml" | "summary:totalErrors=5,summary:totalWarnings=5,summary:productValidation:failed=1,summary:messageTypes:error.label.invalid_object_definition=1,summary:messageTypes:error.label.schematron=2,summary:messageTypes:error.table.field_value_data_type_mismatch=2,summary:messageTypes:warning.label.context_ref_mismatch=5" |
 | 416 | 3 | "github416" | "-R pds4.label -t {datasrc}/phe_misc_temperature_reference_20190524.xml" | "summary:totalWarnings=5,summary:messageTypes:warning.label.context_ref_mismatch=5" |
 | 416 | 4 | "github416" | "-R pds4.label -t {datasrc}/phe_misc_temperature_reference_20190524_invalid.xml" | "summary:totalErrors=866,summary:totalWarnings=293,summary:productValidation:failed=1,summary:messageTypes:error.label.invalid_object_definition=1,summary:messageTypes:error.label.schematron=2,summary:messageTypes:error.table.field_value_data_type_mismatch=575,summary:messageTypes:error.table.missing_CRLF=288,summary:messageTypes:warning.label.context_ref_mismatch=5,summary:messageTypes:warning.table.field_value_format_specifier_mismatch=288" |
-| 408 | 1 | "github408" | "-R pds4.bundle --skip-content-validation --skip-context-validation -t {datasrc}/valid/bundle_insight_seis.xml" | "summary:totalWarnings=14,summary:productValidation:skipped=2,summary:messageTypes:warning.integrity.member_not_found=14" |
-| 401 | 1 | "github401" | "--skip-context-validation -R pds4.bundle -t {datasrc}/invalid/bundle_kaguya_derived.xml" | "summary:totalErrors=5,summary:totalWarnings=2,summary:productValidation:failed=5,summary:productValidation:skipped=1,summary:messageTypes:error.label.schema=1,summary:messageTypes:error.table.records_mismatch=1,summary:messageTypes:error.validation.invalid_field_value=3,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.unreferenced_member=1" |
+| 408 | 1 | "github408" | "-R pds4.bundle --skip-content-validation --skip-context-validation --skip-strict-collection-membership -t {datasrc}/valid/bundle_insight_seis.xml" | "summary:totalWarnings=14,summary:productValidation:skipped=2,summary:messageTypes:warning.integrity.member_not_found=14" |
+| 401 | 1 | "github401" | "--skip-context-validation --skip-strict-collection-membership -R pds4.bundle -t {datasrc}/invalid/bundle_kaguya_derived.xml" | "summary:totalErrors=5,summary:totalWarnings=2,summary:productValidation:failed=5,summary:productValidation:skipped=1,summary:messageTypes:error.label.schema=1,summary:messageTypes:error.table.records_mismatch=1,summary:messageTypes:error.validation.invalid_field_value=3,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 392 | 1 | "github392" | "-R pds4.label --skip-context-validation -t {datasrc}/test1_valid.xml" |  |
 | 392 | 2 | "github392" | "-R pds4.label --skip-context-validation -t {datasrc}/test1_invalid.xml" | "summary:totalErrors=1,summary:productValidation:failed=1,summary:messageTypes:error.table.field_value_overlap=1" |
 | 392 | 3 | "github392" | "-R pds4.label --skip-context-validation -t {datasrc}/INVALID_odf07155_msgr_11.xml" | "summary:totalErrors=2,summary:productValidation:failed=1,summary:messageTypes:error.table.bad_field_read=1,summary:messageTypes:error.table.field_value_overlap=1" |
@@ -92,7 +92,7 @@ Feature: < 3.6
 | 375 | 1 | "github375" | "-R pds4.bundle --skip-content-validation --skip-context-validation -t {datasrc}/h/bundle_gbo.ast.primass-l.spectra.xml" |  |
 | 373 | 1 | "github240" | "-R pds4.bundle --skip-product-validation --skip-context-validation --skip-content-validation --skip-context-validation -t {datasrc}/valid/bundle_kaguya_derived.xml" | "summary:totalWarnings=5,summary:productValidation:skipped=10,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 373 | 2 | "github240" | "-R pds4.bundle --skip-product-validation --skip-context-validation --skip-content-validation --skip-context-validation -t {datasrc}/invalid/bundle_kaguya_derived.xml" | "summary:totalWarnings=8,summary:productValidation:skipped=10,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1,summary:messageTypes:warning.sub_directory.unallowed_name=3" |
-| 368 | 1 | "github368" | "-R pds4.bundle --skip-context-reference-check --skip-product-validation -t {datasrc}/valid//bundle_kaguya_derived.xml" | "summary:totalWarnings=3,summary:productValidation:skipped=5,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.reference_not_found=1,summary:messageTypes:warning.integrity.unreferenced_member=1" |
+| 368 | 1 | "github368" | "-R pds4.bundle --skip-context-reference-check --skip-product-validation --skip-strict-collection-membership -t {datasrc}/valid//bundle_kaguya_derived.xml" | "summary:totalWarnings=3,summary:productValidation:skipped=5,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.reference_not_found=1,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 367 | 1 | "github367" | "--skip-context-validation -R pds4.bundle -t {datasrc}/bundle_kaguya_derived.xml" | "summary:totalErrors=8,summary:totalWarnings=19,summary:productValidation:failed=2,summary:messageTypes:error.file.not_jpeg_compliant=2,summary:messageTypes:error.file.not_png_compliant=2,summary:messageTypes:error.label.duplicate_identifier=1,summary:messageTypes:error.label.missing_file=2,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_encapsulated_postscript_mimetype=1,summary:messageTypes:warning.file.not_gif_mimetype=1,summary:messageTypes:warning.file.not_html_mimetype=2,summary:messageTypes:warning.file.not_latex_mimetype=2,summary:messageTypes:warning.file.not_mp4_mimetype=2,summary:messageTypes:warning.file.not_msexcel_mimetype=1,summary:messageTypes:warning.file.not_msword_mimetype=1,summary:messageTypes:warning.file.not_referenced_in_label=2,summary:messageTypes:warning.file.not_tiff_mimetype=2,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 367 | 2 | "github367" | "--skip-context-validation -R pds4.bundle -t {datasrc}/bundle_kaguya_derived.xml" | "summary:totalErrors=8,summary:totalWarnings=19,summary:productValidation:failed=2,summary:messageTypes:error.file.not_jpeg_compliant=2,summary:messageTypes:error.file.not_png_compliant=2,summary:messageTypes:error.label.duplicate_identifier=1,summary:messageTypes:error.label.missing_file=2,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_encapsulated_postscript_mimetype=1,summary:messageTypes:warning.file.not_gif_mimetype=1,summary:messageTypes:warning.file.not_html_mimetype=2,summary:messageTypes:warning.file.not_latex_mimetype=2,summary:messageTypes:warning.file.not_mp4_mimetype=2,summary:messageTypes:warning.file.not_msexcel_mimetype=1,summary:messageTypes:warning.file.not_msword_mimetype=1,summary:messageTypes:warning.file.not_referenced_in_label=2,summary:messageTypes:warning.file.not_tiff_mimetype=2,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 367 | 3 | "github367" | "--skip-context-validation -R pds4.bundle -t {datasrc}/bundle_kaguya_derived.xml" | "summary:totalErrors=8,summary:totalWarnings=19,summary:productValidation:failed=2,summary:messageTypes:error.file.not_jpeg_compliant=2,summary:messageTypes:error.file.not_png_compliant=2,summary:messageTypes:error.label.duplicate_identifier=1,summary:messageTypes:error.label.missing_file=2,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_encapsulated_postscript_mimetype=1,summary:messageTypes:warning.file.not_gif_mimetype=1,summary:messageTypes:warning.file.not_html_mimetype=2,summary:messageTypes:warning.file.not_latex_mimetype=2,summary:messageTypes:warning.file.not_mp4_mimetype=2,summary:messageTypes:warning.file.not_msexcel_mimetype=1,summary:messageTypes:warning.file.not_msword_mimetype=1,summary:messageTypes:warning.file.not_referenced_in_label=2,summary:messageTypes:warning.file.not_tiff_mimetype=2,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
@@ -224,7 +224,7 @@ Feature: < 3.6
 | 9 | 6 | "github09" | "--skip-context-validation -t {datasrc}/val9b.xml" |  |
 | 7 | 1 | "github7" | "--skip-context-validation -t {datasrc}/ch2_sar_ncxs_20090107t163003745_d_sli_xx_fp_hh_pb1_19111.xml" |  |
 | 6 | 1 | "github6" | "--skip-context-validation -R pds4.bundle {datasrc}/invalid/bundle_kaguya_derived.xml" | "summary:totalErrors=8,summary:totalWarnings=14,summary:productValidation:failed=2,summary:productValidation:skipped=6,summary:referentialIntegrity:failed=5,summary:messageTypes:error.file.name_has_invalid_characters=6,summary:messageTypes:error.file.unallowed_base_name=1,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_referenced_in_label=7,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=2,summary:messageTypes:warning.label.schematron=1" |
-| 6 | 2 | "github6" | "-R pds4.bundle --skip-context-validation {datasrc}/invalid/bundle_kaguya_derived_7.xml" | "summary:totalErrors=8,summary:totalWarnings=15,summary:productValidation:failed=2,summary:productValidation:skipped=6,summary:referentialIntegrity:failed=5,summary:messageTypes:error.file.name_has_invalid_characters=6,summary:messageTypes:error.file.unallowed_base_name=1,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_referenced_in_label=7,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=3" |
+| 6 | 2 | "github6" | "-R pds4.bundle --skip-context-validation --skip-strict-collection-membership {datasrc}/invalid/bundle_kaguya_derived_7.xml" | "summary:totalErrors=8,summary:totalWarnings=15,summary:productValidation:failed=2,summary:productValidation:skipped=6,summary:referentialIntegrity:failed=5,summary:messageTypes:error.file.name_has_invalid_characters=6,summary:messageTypes:error.file.unallowed_base_name=1,summary:messageTypes:error.pdf.file.not_pdfa_compliant=1,summary:messageTypes:warning.file.not_referenced_in_label=7,summary:messageTypes:warning.integrity.member_not_found=1,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=3" |
 | 6 | 3 | "github6" | "-R pds4.bundle --skip-context-validation {datasrc}/valid/bundle_kaguya_derived.xml" | "summary:totalWarnings=7,summary:messageTypes:warning.file.not_referenced_in_label=2,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
 | 5 | 1 | "github5" | "-R pds4.bundle --skip-context-validation -t {datasrc}/invalid/bundle_kaguya_derived.xml" | "summary:totalErrors=7,summary:totalWarnings=13,summary:productValidation:failed=2,summary:productValidation:skipped=6,summary:referentialIntegrity:failed=4,summary:messageTypes:error.file.name_has_invalid_characters=5,summary:messageTypes:error.file.unallowed_base_name=1,summary:messageTypes:error.label.missing_file=1,summary:messageTypes:warning.file.not_referenced_in_label=6,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=2,summary:messageTypes:warning.label.schematron=1" |
 | 5 | 2 | "github5" | "-R pds4.bundle --skip-context-validation -t {datasrc}/valid/bundle_kaguya_derived.xml" | "summary:totalWarnings=6,summary:productValidation:skipped=6,summary:messageTypes:warning.file.not_referenced_in_label=1,summary:messageTypes:warning.integrity.pds4_version_mismatch=1,summary:messageTypes:warning.integrity.reference_not_found=3,summary:messageTypes:warning.integrity.unreferenced_member=1" |
diff --git a/src/test/resources/github1601/bundle_test_1601.xml b/src/test/resources/github1601/bundle_test_1601.xml
new file mode 100644
index 000000000..8ab712744
--- /dev/null
+++ b/src/test/resources/github1601/bundle_test_1601.xml
@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<?xml-model href="https://pds.nasa.gov/pds4/pds/v1/PDS4_PDS_1B00.sch" schematypens="http://purl.oclc.org/dsdl/schematron"?>
+
+<Product_Bundle xmlns="http://pds.nasa.gov/pds4/pds/v1"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://pds.nasa.gov/pds4/pds/v1 https://pds.nasa.gov/pds4/pds/v1/PDS4_PDS_1B00.xsd">
+    <Identification_Area>
+        <logical_identifier>urn:nasa:pds:test_1601</logical_identifier>
+        <version_id>1.0</version_id>
+        <title>Test Bundle for Issue 1601</title>
+        <information_model_version>1.11.0.0</information_model_version>
+        <product_class>Product_Bundle</product_class>
+        <Citation_Information>
+            <publication_year>2024</publication_year>
+            <description>Test bundle for issue 1601 - member_not_found default error behavior.</description>
+        </Citation_Information>
+        <Modification_History>
+            <Modification_Detail>
+                <modification_date>2024-01-01</modification_date>
+                <version_id>1.0</version_id>
+                <description>Initial version for test</description>
+            </Modification_Detail>
+        </Modification_History>
+    </Identification_Area>
+    <Bundle>
+        <bundle_type>Archive</bundle_type>
+    </Bundle>
+    <Bundle_Member_Entry>
+        <lidvid_reference>urn:nasa:pds:test_1601:data::1.0</lidvid_reference>
+        <member_status>Primary</member_status>
+        <reference_type>bundle_has_data_collection</reference_type>
+    </Bundle_Member_Entry>
+</Product_Bundle>
diff --git a/src/test/resources/github1601/data/collection_data.xml b/src/test/resources/github1601/data/collection_data.xml
new file mode 100644
index 000000000..1527dace2
--- /dev/null
+++ b/src/test/resources/github1601/data/collection_data.xml
@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<?xml-model href="https://pds.nasa.gov/pds4/pds/v1/PDS4_PDS_1B00.sch" schematypens="http://purl.oclc.org/dsdl/schematron"?>
+
+<Product_Collection xmlns="http://pds.nasa.gov/pds4/pds/v1"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://pds.nasa.gov/pds4/pds/v1 https://pds.nasa.gov/pds4/pds/v1/PDS4_PDS_1B00.xsd">
+    <Identification_Area>
+        <logical_identifier>urn:nasa:pds:test_1601:data</logical_identifier>
+        <version_id>1.0</version_id>
+        <title>Test Data Collection for Issue 1601</title>
+        <information_model_version>1.11.0.0</information_model_version>
+        <product_class>Product_Collection</product_class>
+        <Citation_Information>
+            <publication_year>2024</publication_year>
+            <description>Test data collection for issue 1601 - member_not_found default error behavior.</description>
+        </Citation_Information>
+        <Modification_History>
+            <Modification_Detail>
+                <modification_date>2024-01-01</modification_date>
+                <version_id>1.0</version_id>
+                <description>Initial version for test</description>
+            </Modification_Detail>
+        </Modification_History>
+    </Identification_Area>
+    <Collection>
+        <collection_type>Data</collection_type>
+    </Collection>
+    <File_Area_Inventory>
+        <File>
+            <file_name>collection_data_inventory.csv</file_name>
+        </File>
+        <Inventory>
+            <offset unit="byte">0</offset>
+            <parsing_standard_id>PDS DSV 1</parsing_standard_id>
+            <records>1</records>
+            <record_delimiter>Carriage-Return Line-Feed</record_delimiter>
+            <field_delimiter>Comma</field_delimiter>
+            <Record_Delimited>
+                <fields>2</fields>
+                <groups>0</groups>
+                <Field_Delimited>
+                    <name>Member Status</name>
+                    <field_number>1</field_number>
+                    <data_type>ASCII_String</data_type>
+                    <maximum_field_length unit="byte">1</maximum_field_length>
+                </Field_Delimited>
+                <Field_Delimited>
+                    <name>LIDVID_LID</name>
+                    <field_number>2</field_number>
+                    <data_type>ASCII_LIDVID_LID</data_type>
+                    <maximum_field_length unit="byte">255</maximum_field_length>
+                </Field_Delimited>
+            </Record_Delimited>
+            <reference_type>inventory_has_member_product</reference_type>
+        </Inventory>
+    </File_Area_Inventory>
+</Product_Collection>
diff --git a/src/test/resources/github1601/data/collection_data_inventory.csv b/src/test/resources/github1601/data/collection_data_inventory.csv
new file mode 100644
index 000000000..51ffc91dd
--- /dev/null
+++ b/src/test/resources/github1601/data/collection_data_inventory.csv
@@ -0,0 +1 @@
+P,urn:nasa:pds:test_1601:data:missing_product::1.0