Are you both running on linux? A linux user on Discord mentioned seeing this bug as well. I'm inclined to think it's linux-only, but haven't identified which distributions might be having this problem.
The most recent update to ZK (that fixed linux crashes) did so by providing a new native linux launcher for steam.
To see if the new launcher is part of the problem, can someone with the audio bug and the necessary prerequisites installed (see the itch
download page for details) try running their version of ZK from a terminal with "mono Zero-K.exe" and check the sound quality there?