[CA11] Autopilot alert - Rudder position info lost

Jeanneau 349 sailboat 2017. In Toronto.
ACU 400 autopilot lost rudder info while sailing with Autopilot on standby.
Alert appears on a75 mfd and rudder position bar is still there but does not
show rudder position. (no red/green bars)
System reboot does not fix the issue.
The next day the rudder position bar is functional after normal boot up.
I cannot find a rudder reference transducer anywhere.
This has happened twice in the last week.
Questions:
1. Is this a software issue? System is one year old.
2. Is it possible that I do not have a rudder reference transducer?
3. I think I have a linear electric drive unit. Does this unit also sense/transduce the rudder position?
Please advise next steps for diagnosis...I don't trust the Autopilot to function
while this alert keeps coming up.

Thanks in advance!