Apologies for the tardy response - there was something I wanted to check out before posting
The short answer is no, I never did resolve the issue. Given that my steering
was not giving me any problems, I let my attempts to check my rudder calibration go, and moved on to other things.
However, I have now realised that although the auto pilot at my helm
station is a ST5000 Plus unit, and that the repeater auto pilot located at my navigation
station inside the boat is a ST6001+. The units are interconnected.
The ST6001+ does not provide for a rudder calibration procedure in the same way as the ST5000 Plus. Instead (under the Dealer Calibration option) it provides for the user to align the rudder position sensor (by having the user centralise the rudder, and then adjusting the display bar on the display to show a centralised rudder), and then setting the rudder limits (by turning the rudder to its full limits and then setting the limits on the display).
My conclusion is that the ST6001+ unit has over-ridden the ST5000 Plus unit (master and slave?), and that this is the reason that the Dockside Rudder Calibration Procedure is missing from my ST5000 Plus.
Although not providing a definitive answer, I hope that this might help you work out what is happening with your ST5000 Plus. Good luck.