That came to me as a regression in Road to Vostok Demo which was tested to be working on Proton 5.13 but frequently crashing on start starting from Proton 6.3. I didn't try to trace what exact changes could leave to the difference in behaviour, maybe there were some changes which showed this up as regression (possibly unrelated to this place at all) or maybe that was just less likely on older versions.
Sorry, I did not notice that MR before, I will close this one then.