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AHRS Changes Mid Flight

Hi All,

Flying in Alt-Hold, hovering in a ~4 square meter area,
Seems like the AHRS changes mid flight (after about ~2:45) and the drone starts drifting strongly - rolling left and pitching up, and I need to fight it with the sticks to keep it in place.
Checked any HW failure, nothing moved nor fell. Motors seems to be flat with frame and props are intact (new). Using D-Shot with ESCs so I don’t see any issue there.

In the log I’ve looked at ATT.DesRoll, ATT.Roll and AHR2.Roll, and the moment of change can be clearly seen there (I think), but I don’t see any event or error message at this point.
I also saw that ATT.Roll and AHR2.Roll behave differently from that point, it’s like one of them knows what is the correct roll angle.

Running the auto analysis shows a bad compass offsets and large mag change during flight, but should that affect the AHRS? and after almost 3 minutes in flight?

Logs and Params:

I must say that it doesn’t always happen at the same time in flight, or at all, but happens quite a lot.
Also, I had this issue before on the same build with copter version 3.6.10 and upgraded to see if it will be solved.

Any insight would be appreciated.

Thanks in advance.

Servers by jDrones