So, even thought they were finally able to recreate the issue at their shop the other day, I was told by Mackie to reflash the mixer to see if that solved it. I did that and tested a few days ago and it didn't "break". This morning I resumed testing and it "broke" 2 minutes in.
Interesting is that I exited the master fader app and there was no change. I wasn't until I paused the song in the music app that it stopped. 10 minutes later I resumed play and the song started playing correctly again. I still had not restarted master fader. FWIW, earlier in the week pausing and unpausing the song after the problem started just toggled between silence and noise. I had to quit the music app and relaunch to get normal audio again.