Hi, I'm having problems calibrating the compass on my phantom 3 standard. I press calibrate in the app and start the calibration process, and hold the drone in the horizontal position, rotate 360 and the lights go green, BUT then I do the vertical 360 and the lights go red and it says "calibration failed magnetic interference" but I'm stood in the middle of a field with nothing for miles, and the only place a magnetic interference can come from is the motors/magnets in the gimbal, why does it do the horizontal alright but not the vertical. Sometimes when I just turn it off and back on again it seems to reset itself and doesn't need calibrating. What am I doing wrong on the vertical, please please help, I'm quite new to drones.