I had a drifting issue with my Mavic Pro that I spent countless months trying to troubleshoot on my own. You name it, I did it to try and fix it. Eventually I sent it in for repairs through DJI's 3rd party repair network (closest was in Mississauga) and it turns out the IMU needed replacing. Got it back last week and after re-binding my controller to the aircraft and doing a compass calibration the bird flies straight.