Sadly, this is all I have figured out to do. As you say, turn the wifi off on the phone. I was having the same issue with Pandora. If on WiFI, it would play one song and then stop, as soon as I opened the phone, the music would begin playng again. If the phone is off wifi, the songs play one after another, no problem, while the phone is locked or in stanby. I will say this, I love my S6 but this is total BS!! I will think twice about another Samsung for my next purchase if they can't get this resolved soon. My Galaxy S 10.5 Tablet works just fine. It's something to do with the new Wifi radio in the S6 I believe. Nothing I have tried works. I got rid of ip6, the hearbeat app, none of it made any difference. I even told Vera to text me an alert to wake the phone up so I could then get the Vera alerts. That was half-a$$ as well. Now, I just stay off wifi unless I am doing a lot of surfing on the phone. Its a real bummer but without the Vera Alerts, my Vera system is pretty weak in my book. I have photo beams and stuff on the property that I need to be accurate and fast alerts. GOOD LUCK!! Please, if you find any solution, share here. I will be sure to do the same. BTW - I too am on Xfinity and use their router for phone/data, no TV, I use direct TV. You can turn off ip6 on the router but it didn't do anything for me. Even after rebooting every device in the entire network.