This happened to me when I was landing my vehicle on the Mun. About 30km above the surface, the camera started drifting, by the time I'm landing, the vehicle is out of site. This might be caused by parts drifting away from the vehicle. I've noticed the vehicle fin started detaching and drifting away from the vehicle, but it is also still part of the vehicle. If I speed up the game and slow it back to a pause, the fin is attached to the vehicle but begins drifting away from the vehicle.