There's a respec error wherever [=display mode=] is defined in the doc, because it's defined in two different specs.
This is actually a result of a recent change I made to both appmanifest and mediaqueries; the definition of "display mode" was moved from CSSMQ (w3c/csswg-drafts#7307) to Manifest (w3c/manifest#1039).
Unfortunately, Respec's database uses Manifest at head (https://w3c.github.io/manifest/#dfn-display-mode) but CSSMQ at a stable version which was last updated in May 2022 (https://www.w3.org/TR/mediaqueries-5/#display-mode). Until CSSMQ's stable version updates to the latest Git head, any link to [=display mode=] will show a duplication error.
Once that is updated, these errors should automatically resolve.