I was having the same problem. I think it's a memory issue on the TV. I don't know what the onboard memory on the TV is but it doesn't seem to be enough. The Xfinity stream app (and all other apps for that matter) would start to hesitate when switching from app to app. You would change the volume and have to wait for it to work. It would freeze then reboot. I happened to have a stand alone ROKU device and have no issues with it. It has a micro SD card slot to expand the memory. When I first got the stand alone device it would do the same thing and the solution, according to roku, was to add an SD card. It solved the problem. This is long winded but I hope it helps.
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