For some reason when flying on autopilot, all of my RXP equipped planes veer off course after FSX has been running for a while.

 

It's not just the 530 (or the Piaggio) but any RXP GPS with any plane's autopilot.

 

When I select NAV with GPSS steering you can see that the plane is slightly right of course.

 

Pressing "D" doesn't work (I thought that might be the issue here - gyro drift bug)

 

Any ideas?

 

I only recall this one with being related to the gyro drift. Pressing D always helped here as it still seems to develop with some gauges, although the FSX options of mine show it being disabled.

 

Is D actually assigned in your key command options?

 

On a wild guess, I could think of a custom magdec.bgl playing a role too. Do you run any updated files? Or does it help when you update the file and backup the old FSX one?

I am using that updated magnetic variation file... I suppose that could be the issue. I'll have to check that out and restore back up