Occasionally, when I’m playing the game, usually if there are a lot of units active at the same time (I was just playing “The Old Tiger” again, for example), a glitch will suddenly cause about half of all sounds, including unit command dialogue and combat clips, to go silent. While the music works, the rest of the sounds will remain absent until I restart the entire game. After this occurs, the sounds will occasionally register, but most of the time they will not.
This issue has been going on since launch, and later patches have not addressed it.