Autopilot looses calibration?

[wmcunninghamii]

I have the ACU 200, EV1 sensor and type 1 linear drive installed on my 30 foot 7500 pound sailboat.

I completed a sail from California to Hawaii with very good performance of the autopilot although performance mode does not like large following seas. When I changed mode to cruising the pilot held course reasonably well in 8 to 10 foot following seas, 25 to 30 Kts wind.

About 2 days out of Hawaii on the return trip the AP was engaged but went hard over to starboard. I rebooted the ACU 200 and control head (they are on separate breakers) several times with no help. I then powered on and switched to my ACU 100 wheelpilot (backup system). The ACU 200 was powered down and was not used for the remainder of the trip.

Upon reaching port on the Mainland I decided to rerun the dockside wizard with the ACU 200 again powered up and interfaced to the system. The ACU 100 was, of course, powered down. I was able to successfully run the dockside wizard, performed the rudder cal successfully and all was good. However, after operating well for several weeks the system once again went hard over and once again I had to re-perform the rudder cal to get the system back. I am also seeing intermittent instances of the ACU not being detected when first powering on the system. I can usually get it back by resetting both instruments and ACU repeatedly but it is certainly flaky.

The fact that the ACU 100 wheel pilot operates successfully when interfaced with the EV1 and never fails to be detected leads me to believe there is something odd going on with the ACU 200.

Can you please provide advice an further troubleshooting?