So I often listen to spotify on my desktop computer at home and my laptop at work.
When I playing music on a separate device and using my phone, often times Spotify opens itself automatically and the music controls show up in my notification bar on mobile. So for example, I'll be playing a game on mobile and try to turn down the volume on the game and end up turning down the music on my PC because Spotify opened suddenly when I did not want it to.
I have to open the app, close the app, and then clear the media controls from my notification bar, and most of the time it just pops right back up immediately. The only thing I've known to work is force stopping the app.

Not enough space to continue typing question. Cool, thanks.