(I already filed an in-game bug report but wanted to see if anyone else was experiencing this.)
I can't pin down exactly when it started happening, but at some point over the past couple of months I noticed that certain sound effects weren't playing correctly when I expected them too. For instance, if I charge my Acheron or Combuster, I hear the sound for swinging it once, and for firing the charge attack, but the charging-up sound in the middle either doesn't play at all or is so quiet that I can't hear it. If I fire a full clip from my Argent Peacemaker, I hear the shot sounds but not the reload at the end. Certain enemy effects like death sounds won't play in large fight situations, which can be a problem when I'm used to relying on audio cues to make sure something died. And most recently I noticed that when the prize wheel appears at the end of a level, the wheel sound plays, but not the little chime when it reveals your prize. Maybe it's selection bias but it seems like this happens most often when two sound effects are trying to play over each other. As far as I know nothing has changed on the hardware/drivers side on my machine.