Just ran into the same problem of video locking up after about 9. Seconds tried a few things but what worked was doing what PhilS suggested. I was on 4K 29.97 switched downed to 25 sho a video then switched back to 29.97 and still working fine. Go figure lol
also have the sticking shutter button so I think I need to buy the X-T3 then send in the X-T2 for repair and keep it for a back up.