For a few weeks, I was unable to play the game and had almost given up. However, I decided to try one more thing:

• I moved the game files to the same partition where my operating system is installed.

Surprisingly, the game has been running flawlessly ever since! If you're experiencing similar problems, I recommend giving this a try.

Additionally, you might want to delete your existing Proton prefix to ensure a clean slate.

• You can usually find and delete it here: /home//.local/share/Steam/steamapps/compatdata/1237950 (be aware that the exact path might differ on your system).