Compass question

[Meta4]

I couldn't figure out why my MM asked for compass calibration on nearly every flight, and then I figured out that my in-ground pool is just loaded with re-bar that extends at least 50' out from the pool. Once I got the MM outside of this envelope, the compass problem was solved!

The drone wasn't asking for calibration at all.
DJI's wording of the warning is very confusing.
It was advising you to move the aircraft or calibrate compass.
In >99% of cases, the only correct action would be to move away from the problem the compass is warning you about.
Recalibrating the compass can't do anything to solve that issue.