It does not compass calibrate with the camera facing down which is depicted in the instructions. It fails the calbration (all the time) when I spin it around 360 degrees. What gives?
Mine works facing up also, but not down as it's supposed to in the directions. I've found I only need to calibrate it after a software update or if I travel to a completely different location quite some distance away. I've heard others say it doesn't need calibrating unless it tells you to... I don't know.
Magnetic interference in close (within 200') proximity could be the problem. Magnetic interference can be caused by a number of different electrical and metallic sources. Try calibrating it in a new location - a few hundred feet or so, away from where you were originally trying to calibrate it.