Not going to make a new ticket for this, but on my device (iPad 8.th gen), this issue persisted after updating to 3.6.3. At least, if we mean the same thing: The audio sometimes randomly gets muted.
That’s the weird thing: I can’t systematically reproduce it! It either happens (pseudo-) randomly, or the pattern is too complex to see. As I said, it always happens to the media that was playing when the app closed, and was then opened on startup. But then, I never know which one comes next. It’s completely unrelated to either shuffle or repeat.
I’m sorry that I can’t really be helpful here, but I’m completely clueless.