a while back i had a problem with the HVAC control panel dying and when it did, everything just stopped working. the dealer's solution was easy, replace it. but it costs $700 and i wasn't so sure that it was the problem. i swapped it with a known working one and the problem still existed so it wasn't the unit itself.
so i thought one of the actuators was bad and tried to isolate it. i unplugged all of them and re-connected them one by one to see which caused the fault.
well, after re-connecting all of them the problem disappeared!!! and it has been over 6 months now without one failure when it used to happen non-stop.
so i don't know what i did but disconnecting them worked.

the bentley service manual was indispensable in this case and paid for itself many times over.