AHRS / HDG issue

[dant]

I'm running in to some weirdness. After around 30-40 minutes of flight my HSI heading starts to drift by +/- 5-10 degrees. This ends up causing a large wind report. It's a lot worse with Rich's LEMO convertor running a lightspeed headset. At first I thought it was backtalk from that however I flew today with a classic dual plug headset and still got it. With the LEMO it would eventually fail the HDG indication.

I also noticed today that my AHRS shows a slight bank as well - just enough to where if I level the plane according to it I start a noticeable turn.

My plane hasn't flown that many times out of annual and cleaning the contacts was one of the things that was done - do both of these seem like things that could be affected by the wing root ground connection to the magnetometer?

Can a bad magnetometer affect the AHRS level?
Can bad magnetometer calibration cause a drift like this or would it be a more constant error?

The on-base avionics shop is backed up months, so I'm hoping to get a plan of attack before scheduling shop work.

TIA

[Leesommer]

I had similar issues and then started getting red x's on the pfd.. replace the magnetometer that didn't help finally replaced the ahrs and it worked no more red x's and everything seems to be level