autopilot keeps going into "No Drive"

[mcbillhawaii]

My ST-70/SX30 autopilot keeps going into "No Drive". When I try to do dockside calibration it goes to Rudder Check and when turning hard to port it alarms and quits with a Rudder Feedback error.

Sometimes when I go back in again it gives a Rudder Angle screen instead of the turn and center. I don't know what angle to set it at.

How can it restore full range to the rudder and reset the center point?

Note: I had to do an emergency cable repair which didn't appear to affect the range of motion, but I'd like to get through dockside setup. The latest software was installed last summer.