Distorted sound in NieR: Automata after several hours of gameplay (524220)

Compatibility Report

• Name of the game with compatibility issues: NieR: Automata
• Steam AppID of the game: 524220

System Information

• GPU: GTX 1070
• Driver/LLVM version: nvidia 410.57
• Kernel version: 4.18.8
• Link to full system information report as Gist: https://gist.github.com/rkfg/b1bbede62bf81935eb3819037bd12bb0
• Proton version: 3.7-7 Beta

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.

Symptoms

Sound starts to stutter and echo after a couple of hours. The echo is extremely low-res, distorted and clipped, more like noise but it certainly reflects the sound the game produces. It can be fixed by restarting the game. PulseAudio version is 12.2. I don't have such issues in other games, including the Proton ones like DOOM, GTA V with no sound problems. However, this is the only Proton game that I played on the TV in Big Picture via HDMI so the sound driver is not Realtek but NVIDIA HDMI. I played a lot of other native games on TV without issues (for many hours in a single session) so it must be something with Proton or the game itself.

Reproduction

Play the game for several hours (like 3-4), for unknown reason the sound becomes distorted at some point. I didn't notice, maybe it happens after entering and exiting the main menu that contains map, inventory, intel, settings etc. Nothing can fix it after that, except restarting the game.

No source file or test is identified. Start by reproducing the three-to-four-hour session with Proton 3.7-7 Beta and the reported HDMI setup, then rerun with PROTON_LOG=1 and inspect the generated steam-524220.log. Done means the sound no longer becomes stuttered, echoed, clipped, or distorted after extended play.