Definitive Edition on Linux

I know there are existing posts about this, but I've tried all the suggestions, as well as those found at the ProtonDB website etc., so thought I'd try asking here.

I have a very strange issue where most of the time, the game boots to the main menu, and then at the same point (judging by where the theme music gets up to!) it crashes back to the desktop. If I'm fast enough during this time, I can get into the menus normally, e.g. campaigns, but it still crashes.

However, without changing anything on my system, very occasionally it seems to get past this crash, and if it does, the game works perfectly (at least in single-player, haven't tried multi yet). So as long as I don't quit the game, I can play to my heart's content!

I'm running under Debian 9. nvidia-driver is at latest available version (418.74) for Debian 9. I have had it work (at random) for various versions of Proton, at one point I successfully played an entire campaign under Proton 5.0.9.

I've tried various changes, such as installing vulkan-utils, different Proton versions and Launch Options, but nothing seems to affect this crashing behaviour.

Perhaps the only pattern is that it seems to work immediately after a patch or hotfix is installed, but then not again after that. Maybe there is some kind of caching issue? Although this could also be mere coincidence.