A new SteamOS update was pushed to the stable branch that fixes sound issues and increases stability and security on Steam Deck.
Fixed an issue causing no sound output in games that open and close audio devices quickly like Super Blood Hockey
Stability and security improvements
This combines updates .18 and .19 from the beta channel. Valve is usually more specific about what "stability and security" fixes include. Between being oddly non+specific and the fact that they pushed this update out as quickly as they did, I have a suspicion they were fixing a significant security issue. So probably best to update as soon as you're able.
The sound fix will be nice for affected games as well. I know Dishonored 2 would lose audio after the deck went to sleep, and that's fixed now. I can't confirm if it was actually this patch that fixed it though, but it's a great fix to have regardless.