M2P - Focus issues

A few weeks ago my M2P drone started producing some video in focus and some not in focus totally randomly so far as I could see. As it was on Auto focus I switched to manual focus plus I was using an ND16 filter on it so wondered if that was affecting the auto focus. This time on manual focus it was fine until I was landing then even on manual it suddenly went out of focus. Other point I noticed was the change over is pretty much on the file break between two files.

You can see a clip where this happens here:

Anyone any ideas on what the issue is?