The little black nonsense a.k.a fluxgate
compass from Raymarine is known to give many headaches.
Newer course computers
use the new non mechanical white discus. It is advertised as 'better'. We will see.
Keep the drive, esp. if you have the GP one. They are no longer available.
Check Webb Chiles blog for failure rates of Ray tiller autopilots. Exceeded only by some solar panels