V2 cameras play back at double speed

For the last two weeks, my V2 cameras play back at double speed, like from the Charlie Chaplin 1920’s silent movie films. The speed was normal for a couple of weeks before that, but it’s been an on-and-off-again problem. I was too busy complaining about missed detections to mention it before - always something! Updating the cameras and the app didn’t work. Anybody got any ideas?