[CA] Type 400 S3G course computer only works in the tropics!

My course computer works fine when it's in the tropics, but not in colder temperatures. Seriously.

After powering up and activating the autopilot, the drive freezes position for 10-15 seconds, then the controller displays a current limit error. Hours later, it starts working normally and continues indefinitely in a normal state. After this failure, if I warm the controller with an electric heater, it returns to a normal working state. Also, if I pre-warm the controller with the heater before powering up the system, the computer functions normally at startup. Systematic troubleshooting eliminated other causes, including removing and bench-testing the M81131 Type 2 short drive.

Is this a familiar problem with a predictable fix, or is it really as weird as it sounds?
Assuming no predictable/reliable fix, what are my options for (hopefully plug-and-play) replacement?

Specs:
Course Computer 400 - E 12055 0520152
with post-manufacture notes indicating
"(S3G), "Added Rate Gyro Processor in 2012" "software updated to V 4.19"

Other system components:
C80 MFD (have E80 ready to install to replace C80)
RD424 Radome
ST60+ Wind
ST60 TriData
ST6002 Controller
Raystar 125 GPS

Thanks, Mike