Set return to home altitude to 20 meters, established home point, P mode, took drone out to 125 feet and 50 ft. high, hit return to home button on controller, it rotated 180 degrees to come back, climbed to over 400 at which point I canceled RTH by pushing button on controller. Have done this twice at different locations. What have i missed in settings. Calibrate compass every time and I calibrated IMU. Seems like it does not know its altitude? Completely open field void of any obstacles