Heading Alignment SPX-30

[Taylor7000]

I have problems with the heading alignment changing and varying up to 30 degrees port and starboard with my SPX-30 pilot. The unit will track properly to a way point and follow a course with no issues. However, when in heading mode the vessel will change course as the heading moves. I can watch this happen on the chart plotter. The vessel indication will stay constant and the chart rotates as the vessel changes heading (verified by oil filled compass). When tracking a course or going to a point the orientation of the vessel on the chart plotter screen rotates. All equipment is Raymarine less than 4 years old all communicating via Seatalk-NG. Installed on a sailboat. No messages or errors. Replaced fluxgate compass with no results. I have had the core pack repaired by Raymarine and it worked properly for a few weeks then started doing it again. I replaced the core pack with a new unit and it worked well for about 6 weeks and it has started doing the same thing. Question: Is this a known issue with the SPX-30? What could be causing the same repeated failure?