Don't give up! One other technique you can try. I really think the processor is not properly asserting the 'P.ON/OFF' signal and it may be thermally related. Grab a can of freeze spray, and after the unit has been on and working for a bit, try using the freeze spray around the processor and associated circuitry. See if you can get it to quit.
And/or.. From a cold start, turn the unit on and use a hair dryer to blow warm air into the processor area and see if the unit responds quicker than with no external heat.
Ok, i buy freeze spray tomorrow and try some more