Apparently some Mavic PRO units are coming with interference-sensitive compass 2, the warranty is solving this problem by replacing Gimbal or Compass 2. The real problem is that some parts of the Mavic are magnetized, preventing the Compass calibration process from being completed.
there is a tool called cfixer that solves the problem, but it is very expensive.
So what I did was buy a tool demagnetizer and used it on all the front metal parts of the drone
https://www.banggood.com/Magnetizer-Demagnetizer-Box-Screwdriver-Tips-Screw-Bits-Magnetic-Tool-p-961755.html?rmmds=search&cur_warehouse=CN
Then I reinstalled the last firmware calibrated IMU and COMPASS and now no error message appears, even the Mavic is much less sensitive to external interference.
f my tip does not work for you, try this little tutorial sometimes, some friends with this problem had to try 2 or 3 times to calibrate the drone correctly.