When I am called upon to help diagnose a problem on a sophisticated machine, history is very important. I ask questions about how it worked before the problem occurred, when it happened, what exactly was going on at the time it happened, etc.
I read thru most of this now and it seems to me your history is it may have always had a slight tendency to make those pixel type and pixel line marks, but not enough to cause you concern - until something happened. The something was another plane flight. Then the marks showed up as major problem. So the difference is the plane ride.
I propose the slight tendency to mark became majorly bad as a result of an air pressure change larger than drone has seen before. How could that have caused the issue? My ears pop, I would theorize at this point that the pressure change caused some kind of molecular pop. I would jump at pixels in the actual sensor but the marks do not appear to be in the same spot each time. Since they move, it is probably not a sensor issue. You say it is worse on videos but in my zipping thru 3 pages here I saw no videos posted. The stills remind me of when weather causes my sat TV picture to loose data; if slight, I think it can make similar smears and marks, and of course they too are random areas of the screen.
If I made myself real small and crawled around your camera pcb, I think I would be looking inside each semiconductor IC in the video path in series with the sensor, having a feeling that that pressure change popped some small corner of silicone along the way. That small section of loose popped silicone is adding the noise seen in the pictures. This seems to justify that it was really 'always' that way, just getting progressively worse since the beginning, but particularly worse with one flight. I wonder, during that flight, do you recall having an exceptionally noticeable pressure change popping your ears?
How's that for a Saturday morning theory? Unless you have a scope and schematic of the camera, you are not likely to be able to poke around and prove or disprove the theory, so replacing the unit or warranty claim seem your only solution.
