Problem with magnetic sensors

I have been fighting issue with my new quad setup.

From the begining I have been fighting irrational actions. First I was using fmu v2.6 and next I grabbed PX4.

From the status display in mission planner I noticed external magnetic sensor showing alternating readings going up and down in no relation to internal sensor. This is related to all three axis.

I changed sensor but the same behaviour.

Any idea

Thordur Ivarsson