P2V fell 403 ft. at a distance of 600 ft. from Home point. Before falling, P2V became unstable and lost signal with RC; flight software was DJI Ultimate Flight. Surprisingly, visible damage was props and prop guards. Landing leg containing compass was slightly compressed with cover pooped off. Replaced props & prop guards but P2V couldn't get off the ground; one side was lifting causing the props on the other side to hit the ground. My initial thought was that the IMU needed calibration. Hooked up the P2V to the Assistant hardware and it stated that the IMU was running hot and to shut it down, let it cool off and retry. That wasn't the case since I knew that it was cool, recalibrated. P2V was able to get off the ground but was unstable; drifting in one direction and up and down. How do I determine what the problem(s) is? Do I need a new compass? Does the GPS module require replacing? Or, is it a motor(s).