This happened recently:
We seem to have an unfortunate case here where a PR that passed tests (#2291) was merged, and then immediately after merging tests on master started to fail (https://github.com/TuringLang/Turing.jl/actions/runs/10281463329/job/28451089388). It's a concurrency problem of some kind, only appears on multithreaded. Haven't dug into it yet.
That's still the case on master. Looking into this now.