I'm facing this issue since I chenged Huavei P9 to Samsung Galaxy 10.
I've tried all sollutions described here, but spotify randomly stops playing anyway. This occures more often when I'm listening something new, some new album. Sometimes when I wait a while, the music starts plaing again. But most often I'm applying a silly sollution:
Setting-> Applications-> Spotify Force Stop. Then I'm running Spotify and the music is playing till the next unexpected stop.
it's actually pretty gross that yoir answer to a simple problem like this is to have the user allow all permissions. contacts. photos. microphone. even though your ceo says they'll never be accessed without permission, its somewhat troubling that the issue of spotify playing after the is closed is to allow spotify to access your entire personal cell phone. thats like being sick and going to the doctor , only to have the doctor require you to give him access to your personal social life that has nothing to do with him getting you better.