[CA] SmartController Problems

[Sailor Nick]

My system is several years old and has been working well until now.
Recently the SmartController malfunctioned and appeared to loose connection to the RF base station.
The controller displayed the message "ERROR" Check Sum Fail 00 0000 00 and then more zeroes. It then says Searching for network, then Press any key, then the screen blinks sometimes a black line shows temporarily then nothing, even the key clicks stop.
After a few moments if I press C it the whole sequence starts again.
By putting the two units close together and continually restarting them both sometimes they connect, when this happens the signal strength indicator is minimal, the date and time are incorrect and by pressing and holding the Select key I can access the menu which appears ok except that I get a No Pilot message.
I cannot get into the Dealer Maintenance program to test the system.
I have tried the "reset" button on the base, no change. The voltage at the base is 12v - 13v in a dry location.