Dynon and AFS tech support must be backed up so here is a question for the gurus.

On my 3 year old AFS built panel, with an ACM and a hall effect sensor for amperage, I have had the readings drop off dramatically lately.
My baseline load in cruise was running about 15 to 20 amps until 3 months ago when it started to give me low current warnings.
The current drops to about 2 amps after about 10 minutes of running regardless of whether in the air on on the ground.
I checked out the B&C 40 amp alternator and it is OK.
Then I put a clamp on amp meter around the power cable next to the hall effect sensor.
Long story short, the hall effect sensor reads 13 to 15 amps lower than the clamp on meter.

Question: Can anyone think of a reason other than a bad sensor that might happen?
I'm reluctant to put in a calibration offset of that large a value.
I probably need to order a new one and swap it out but thought I'd ask prior to the effort and gymnastics involved in doing that.
BTW: I do know about the recent sensor letter and mine is not affected, I do have the screws in place on it.
Thanks in advance.
Mike H