Harvesting delays by 15 minutes every day

[dev-rke]

I successfully build a harvesting environment via dcat extension, running several harvesting jobs.

Unfortunately a harvester is delaying it's start every day by 15 minutes.

Example of start times of my harvester jobs:

2025-01-08T13:00:10
2025-01-07T12:45:10
2025-01-06T12:30:16
2025-01-05T12:15:16
2025-01-04T12:00:16
2025-01-03T11:45:12
2025-01-02T11:30:05
2025-01-01T11:15:12
2024-12-31T11:00:05
2024-12-30T10:45:16

My cronjob is running via */15 * * * * ckan harvester run, which is correct in my opinion.

How may i configure the harvesters to start at the same time every day, e.g. at 03:00AM?
That causes issues when other systems i am harvesting from are under regular load - so i would like to move the harvesting time into the night.

Thank you and have a wonderful year 2025.