The frame rate stutter may be fixed with Proton 5.13-2 and having vsync disabled. It has at least been mitigated, I just played for and hour and didn't have an issue. Previously I had to restart every half hour or risk getting severe frame rate drop. I will have to test for a bit longer than an hour to be sure.
Another issue the game will not close gracefully even with 5.13-2 (also the same with 5.13-1 and 5.0-10) When you confirm the exit in game the game freezes and has to be killed with the "Stop" button the Steam's library page. The most Proton that closes successfully is 4.11-13, but if I remember right 5.0 was closing correctly in prior versions, maybe 5.0-8 and below
proton 5.13-2x1 2020-11proton 5.0x1 2020-11
Compatibility Report
System Information
I confirm:
Symptoms
Game runs as well as windows on both proton 5.0 and 5.13 but after 30 minutes or so of gameplay there start to be framerate drops, these get severe pretty quickly and within 10 minutes it becomes unplayable with stutters
Reproduction:
Play game for an extended period of time