Flatten Timeline, Lose Audio

I have been having an issue since the release of the update that every time I flatten unused video tracks in the cleanup, that I lose audio playback. The audio tracks are there, unmuted, unharmed, just don't hear any audio in playback when playing the timeline. When I Undo and go back to the unflattened timeline , I hear the audio just fine. I Redo and go back to flattened state, lose audio again. Anyone experience this?

I haven't had this happen with the Flatten command, but every now and then I do lose audio playback in Resolve.

Somehow my audio preferences get changed, and a manual change back always fixes it.