This doesn't happen all the time, but I have some earbuds and I often try to play where I can't listen to the audio out loud. If the game is already running, and I pair with the earbuds, half of the audio stops playing. (this also happens with another bluetooth device I have for my car, so it's not isolated to the earbuds themselves, though it does not seem to happen on my iPad Air 4 (that I can recall), it happens on my Pixel 4XL.

Anyways, steps to reproduce:

If game running:
1. Connect over bluetooth your earbuds, speaker, whatever
2. music stops playing, but "UI noises" continue. (like, clicking on different parts of the interface, opening/closing menus) but the voiceovers and background music, battle music, etc do not play.

You can fix it by relaunching the app, and then it's fine, but it's pretty fucking annoying. Disconnecting the bluetooth headset does not fix the audio when this happens, you have to relaunch the whole app.