Timing/sync on one camera

Hi, I'm runnning motioneye 0.42.1 on a raspberry pi 3 model B plus rev 1.3 (with raspbian 10) and am having issues with 1 out of my two cameras. One camera is completely fine but the second one is running at a reduced speed. What I mean by this is that the camera's on screen text showing the time starts out the same as the motioneye time overlay but over time becomes further and further behind. It's very strange as it's not conventional lag where it's always x seconds behind, it actually gets worse the longer it runs for. This camera is a higher definition than the first but I've tried dropping all the quality settings, FPS and resolution but none of these have any impact. I would have thought the 3 B plus could handle two cameras at 720p..

Any ideas?

Thanks, Josh