Having the exact same issues.
-Swipe for control center
-Drag the media volume bar all the way down
-Swipe away control center
-Go right back to swiping for the control center
-IPhone turned the media volume back up 1/4 of the way.
This is frustrating when I’m in an area of silence and can’t trust my iPhone to keep the sound muted. All settings suggestions have been tried, but none of it works.
I’ve done:
1) Settings > Accessibility > Face ID > turn everything off
2) Restarted iPhone
3) This happens with no bluetooth device connected.
4) There’s no VPN
Im not finding anything on the web, so I hope someone in here cracked the issue or Apple notices how inconvenient this is and fixes it.