When I'm in-game (using steam and proton-ge or just proton) and have Discord open, I sometimes (or better often, just not predictable), have no sound. I can't hear the system-sound anymore (including discord) but my microphone works fine, meaning others in a discord call for example can still hear me. When I have Spotify open and music running the issue appears less often. But when it appears Spotify seems to not being able to play a song. There is a small white popup with roughly the text "current song not playable". The same in YouTube, just that the video is not loading (even when it has buffered). When I close my game and Discord the sound is back and Spotify/YouTube is able to play the current song/video again. Also, when I change the Audio Output from my Headset to my music speakers, then the sound is available again (when changing back to the headphones it is stuck again).
The Headphones mentioned are Sennhaiser GSP 960 and the music speakers are the Logi MX Sound. I am currently running stable NixOS, but the issue also appeared on an Arch Linux install.
Did anyone of you experience the same issue as me and found a fix for that, or know how I can debug the problem or can help debug the issue?