[Sloved]Compass issue about copter3.4.4

hi all,
I just updated my cuav pixhack to copter3.4.4 firmware and discovered the mag EKF was abnormally when flying.
I had tried to re-calibration compass, but no luck.
The mag issue does not occur in firmware 3.4.2.
How can I solve it? Any advise is welcome~

LOG: 55.zip (2.3 MB)

Mag in firmware 3.4.2 is good

More info:
MAG1 is extenal M8N GPS and HMC5983 compass,
MAG2 is pixhack internal compass.

MAG2 result looks good, extenal compass looks abnormally, but both running good in firmware copter 3.4.2

The root cause is the battery had come adrift from the GPS module.