I have a lot of projects that use the same resource. They all trigger in the evening and just make their way through the queue one after the other. Occasionally a test fails, and the logs show that two projects are both running at the same time after acquiring the resource.

The Jenkins jobs that are overlapping are matrix jobs. They make use of the Label Expression setting to control which Jenkins nodes they run on.

I can't make this happen on demand. I've tried triggering simultaneous matrix projects from the web UI, through scheduling, and via the REST API. Are there any Jenkins logs I can provide to help narrow this down?