This happened with my old Hero 7 Black. Press to stop a recording and the screen and camera froze while the timer kept counting up. Resetting sometimes worked, popping the battery would usually corrupt that video and sometimes the previous videos on the card. It was worse in warm/hot weather. Did multiple firmware updates over a few micro sd cards, no change.
Returned to the retailer, just out of 1 year warranty, had it sent away for assessment/repair expecting to pay.
2 months later the case had not progressed on the repair end, so the retailer gave me a full refund. Put it into a Hero 8 Black which was the same price by that time. Great camera.