me too, it happened twice using "music folder" app.
it happened since I've oreo 8.1 stable version.
I've tried the trick suggested but it doesn't work for me, after 30 minutes the app music folder stopped playing the songs so I'm forced to enter in the app again and start it
Same issue, however, it happened with 8.0 for me as well. Spotify and Youtube also stop at around 30 sec, and what's really annoying is that when I restart play, it often does at a much higher volume.
Damn, I don't want my ears to ring.
Same issue here! This is very common problem. You have to to fix it.
I also have this problem.