Yesterday while getting ready to film some corn fields for a farmer my vision app gave me a message of "Compass Calibration Needed". I was not able to turn on video, take pictures, or set up a flight path. I went home and did an IMU calibration. Went back to corn field and everything was fine. Today, different corn field same message. All lights on bird show that it is ready to fly but vision app says compass calibration needed. Went home and every thing was fine. Checked IMU's on PC and compass mod is at 1300-1350. Plugged MC into assistant on laptop and compass mod is 1175-1185. My status on the imu menu says idle, where as on PC it was always ready. I have had no recent hard landings. I havent found any info on the "compass Calibration needed" message on vision app. Do I need to do a magnet calibration?