It seems to be all aircraft, prop, jet, etc. When the aircraft is on the ground, it’s nice and smooth. Once in the air though, it’s violent shakes. They aren’t tiny shakes by any means so I doubt it’s engine vibrations.
Try following an aircraft in mid flight using the drone and choosing CTRL Pg Up, and then zoom in to the aircraft so that you’re around 100 feet away. I’d be interested to know if you see the aircraft you’re following shaking violently.