Whispers of a Machine (631570) -- sometimes it starts, sometimes it doesn't

Compatibility Report

• Name of the game with compatibility issues: Whispers of a Machine
• Steam AppID of the game: 631570

System Information

• GPU: AMD Radeon VII
• Driver/LLVM version: Mesa 19.1.0+aco+git1573122507-2e64afa5e39-1bionic2
• Kernel version: 5.0 [Ubuntu 18.04 HWE]
• Link to full system information report as Gist:
• Proton version: see below

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

steam-631570_failed.log.gz
steam-631570_working.log.gz

Symptoms

If the game launches, it runs perfectly. However, often as not it'll switch to "running" state in Steam, but never actually launch, no audio, no video. Clicking STOP on the Steam UI doesn't work, one has to kill Whispers.exe, then try again. Sometimes it works a couple of times in a row, sometimes it fails just as often.

Reproduction

Try to launch the game.

I've noticed this problem since the upgrade to 4.11-8 (though I've only started to play recently and might just have gotten lucky with 4.11-7). FWIW, 4.2-9 is the same, 4.19-GE-1 seems to work (>5 consecutive successful launches).

Start by comparing the attached steam-631570_failed.log.gz and steam-631570_working.log.gz files, then reproduce launches with the listed Proton versions. Done would require a confirmed cause or reproducible regression that points to an actionable Proton change.