I've been experiencing this also while watching Netflix. The video will pause for 15-30 secs with the audio continuing. Eventually it synchs back up further up in the scene. Amazon video won't play at all. Do you think this is a case of the apps not yet jiving with Android 7.1? Or possibly some bad phones? Mine is a Pixel XL from Verizon. I'm still within my 14 day to return if a bad unit. Anyone have an idea what could be going on?