Since updating Mission Planner (Windows) to 1.3.2 and 1.3.3 I and a number of my associates have not been able to complete Mag calibration.
The new dialogue box appears when selecting Calibrate, and it rotates in sympathy with the APM 2.5/6. But no matter for how long you work it the calibrate routine does not complete.
If you abort the Calibrate routine and check the APM2.5/6 against a real compass the two tally. APM 2.5/6 is correctly indicating the points of the compass.
This issue has only arisen since 1.3.2 onwards.