I've encountered something similar: traffic light controllers (which is a big part of my day job) with a bad lamp switch board.
The lamp switch board was disassembled, and then it's connector was cleaned and rubbed with connection grease.
After that the board was put back in to the controller, and tadah' it was working ok again.
(these are the mysteries of the ITC-2 controller)The connections are always worth a while to check, when problems occur.