@hoogs I had the same issue. I did not find a fix. The only thing I found out is, that it did not happen if I play the music via bluetooth. I bought a cheap bluetooth receiver for my headphones and used it like this for a few weeks.
Because I had other issues with anbox (regarding camera freezes, nexus 5), I removed anbox again.
but I tried this before and it does not fix the issue. As i mentioned above, even before I install anbox-ubuntu-touch I have the issue with the camera. So it has to be something in that anbox img that causes this issue.
Then one day later it freezes again.
All I did in between was: