511 rudder feedback error



I have a 511 system ( not installed by me) that is giving rudder feedback error.
It has worked fine for the few years I have owned the boat.
sometimes it starts an auto heading for less than a minute before giving error message
Any place to start troubleshooting?
Thank you,

control 511
Processor type FAP-5002 C# 8044-3883
Drive unit Balmar S power unit
Start with the rudder feedback.
With the 511 on in standby push the standby button until you see the rudder angle. Does it change when you move the wheel? If it does, is it smooth in its movement? If you see no movement in the display then you will need to check back at the rudder to see if the linkage is attached to the rudder post.

Let us know what you find.
just got back to the boat
When I turn the wheel the display corresponds. It seems to follow correctly in both directions
the linkage is attached to post and appears to be connected as normal
If the rudder angle changes smoothly from port to starboard then it sounds that it might be OK. When you energize the port and starboard buttons while in standby at the dock does the rudder go hard over to hard over? You can also see if the error occurs while at the dock by going into auto and changing the heading set by about 5 degrees.

There could be an issue with the drive unit as I am not familiar with it.