I flew my Phantom 2 + v3 over the weekend 100 miles or so from my home area. No issue with compass calibration, and no issue when I got back home. But yesterday I got the message on the App to calibrate as soon as I fired up WiFi. It took multiple tries, and on one try that was successful, when I turned WiFi back on, the App still said to recalibrate. The flight I had when everything looked good to go was fine. Rock steady hovering. Any ideas as to why the app was doing that?