Did you try giving them unrestricted access to battery? My music app used to stop playing if I went into a different app till I did that. Also, I have had to update my Google play services app a couple of times recently, that can affect how apps work as well, it was actually waiting to be updated but sometimes it doesn't necessarily so I just press uninstall, when that's done, I update it again in case something was off with the previous update. And another thing to try, if you don't already, try going into play store, then settings, about, play store version, it gives the option to update it, maybe try that as well? It will tell you if it's on the right update
