I had this problem today for the first time. I was just reading the xda app when it happened.
I was not charging the phone at the time.
I don't have spotify installed.
I have never accessed movie-maker.
I think the browser might also have been open at the time with the lab features turned on.
Another open app. that was open is an extremely simple one called Next Train Ireland
I do have the volume fix installed. Initially, I thought it might have something to do with that.
I have no intention of losing my lovely GN for the sake of a bug! -- Unless it starts to happen every day...