So I have a Precision Vertical Card Compass that is showing very large deviations on certain headings not accounted for by the compass deviation card. It agrees with the card on other headings. I need to get a working compass before my IR check ride so I can practice compass turns.  I think the unit is around 7 years old and  predates my purchase of the aircraft but it was calibrated ~2 years ago when my panel was redone.  It was true to the deviation card at that time, and it has the correction