I don’t have such a problem temporarily
Hmm, ok. I had missed this thread said Safari. My apps are not played through Safari. But all 3 of my apps published to the App Store have this problem. But it does not follow the same pattern. Sometimes I have to do the lock screen-->unlock several times before the audio dissapears and sometimes it happens during the first lock-->unlock.
Have you tried locking and unlocking several times to see if it might trigger the issue?