My LG X Power volume keeps resetting to 2
I figured it out.  

It was the "Call Blocker" app from AndroidRock.

The problem went away after I uninstalled the app.  To be sure, I reinstalled it, and the problem came back.  I tried this about 3 or 4 times to confirm.

https://play.google.com/store/apps/details?id=com.androidrocker.callblocker&amp;hl=en