In the test output, it looks like this:
After that, the worker does not do anything anymore, and at the end MTR complains
We know it's rpl.rpl_mdev382 because it's the last test in the corresponding server error log:
The test only does restart once, and does it seemingly accurate: it writes "wait", then shuts down the server, then removes the file, then writes "restart".
And removing the file fails claiming that it does not exist.
I could not reproduce it, but it's not the first time I see it (not so easy to find since it won't show up in the cross-reference report).
For now, I don't see why it's happening.