Autohelm st4000 tiller

[930chef]

I have a Cal 34 with the Autohelm st4000 tiller that works fine. The small screen on the bulkhead sometimes reads fine, then becomes unreadable.
Sometimes if I manipulate the screen, it will go back to compass readout, then back to random figures.
Has anyone had this problem?
Is there anyone that repairs the head unit on these old systems.
Is it possible it's a poor connection on the back of the unit?
I'm not electronically inclined, but I'm open to suggestions to troubleshoot.
Thanks in advance for your help,
Kevin