I've had heading sensor irregularities with my Solix at the console. I could never find the source of any interference with the charging system or the motor. It was only 7-10 degrees or so. I used a standard compass and my cell phone compass with a magnetic field sensor that did not display and magnetic interference. However, the two never matched. After moving the standard compass around inside the rear hatch it went nuts near my small toolbox. And believe it or not. It was a magnetic screwdriver handle.
I thought I would pass this along since for months I was chasing what i thought was complicated electrical interference issue. It was as simple as a screwdriver handle with a magnetic tip to hold the various bits. Moved tool box to the port side and all was stable.