[CA] [CA11] ST 5000+ autopilot issues

[dle44rain]

The autopilot on my flybridge trawler has been steering the vessel in slow ~30° S-curves to port and then to starboard when placed in "auto" mode. The vessel will maintain the average magnetic heading while slowly steering the vessel in S-curves over the course.
I followed the "Operating Sense" instructions in the manual at dockside:
Press AUTO
Press the "+10 key"
The rudder turned. I then pressed the "-10 key" and the rudder started to move but almost immediately stopped after a clicking/grinding sound occurred. The result is that the steering wheel will only turn counterclockwise now even with all electronics turned off. The autopilot operates a hydraulic pump. Both wheels will turn counterclockwise but not clockwise.
I would appreciate any advice about what should be done to solve these issues.
Thanks.