Random volume changes

[danmeek]

I'm running Android Nougat on a Moto X Style. When I play Spotify through the device speakers, the playback randomly shifts volume - starting normal, going very quiet, suddenly loud then quiet again. This only happens with Spotify playback: other audio apps are not affected. I have disabled equaliser in Spotify and on the device but it still occurs. It's a big variance - from close to max volume to nearly inaudible. This has been happening about 2 months.

Does this happen to anyone else?