This has been going on for some time for me, but thought it was a beta bug. It is still happening with 13.1.2 though. Sometimes while a video is playing in the background it will randomly start over. I will be in another app altogether and it will happen. I thought I might have been hitting something on my Watch to cause it, but I'm not wearing my watch today and it just happened while typing a text. Anyone else have this issue or know a solution?