I have started experiencing the exact same problem since I changed my headphones and added a sound card. After a very variable number of rounds my headphones will go mute. It seems completely random as sometimes I can play hours without any problems and sometimes it happens right away. Quitting the game doesn't solve the problem, neither does closing my windows session or unplugging/replugging the headphones, which is intriguing. As Hirlok said, the only thing I found that solves the problem is rebooting. After quitting the game, windows tells me that everything works fine, as I get the visual indicator that a sound is being played when e.g. I change the volume. To the best of my knowledge, cRPG with WSE2 is the only game that does this, although I did not try reproducing it in Native or in cRPG without WSE2 yet.