Everyone talks about doing the IMU calibration, but my PV2 with updated firmware and newest assistant software has never let me do an IMU calibration, it always reports "not needed...." when I click on the button. Is this normal? Is the IMU calibration done as part of the advanced calibration (I ended up doing the advanced hoping it did). My compass is calibrated, no crashes, but my PV2 does the toilet bowl circling on hover, about a 10 ft diameter even with 11 sattelites in gps mode.