You might try running some wire. Perhaps one of the traces on the board has a hairline break. I would start running the ground from the 3 wire receptacle to the Voltage regulator on the DBC, and then to the ground point on the Chip. Without a proper ground all kinds of things can start happening

Perhaps the temperature is playing into the trace problem. Maybe when it warms up something opens up and a connection is broken , By paralleling the key connections with wire you may solve the issue.?? Just something to try.