SPX 30 Drive Stop Issue

[SVNeko]

Hi, I have a hydraulic autopilot motor (Lecomble &Schmitt) that is controlled by a SPX30 computer and a P70 control head (although I mostly control the pilot from an e127). Lately, the AP has been dropping out citing "Drive Stopped". When I re-engage it it sits for a while saying "Setting to Auto" then either engages or drops. If it engages, it soon drops again, saying Drive Stopped.

At anchor I can keep it engaged for a minute and when I use it to turn the rudder, nothing happens. The rudder is free to turn, so no blockage. The rudder reference unit seems to work because the electronic rudder reference shows it turning when I manually turn the wheel. The drive seems to work because when I apply power to the motor output leads at the computer, the drive turns the rudders. So, it seems to me that the computer is faulty, but it is only a couple years old and I had it checked a year ago.

Any ideas?