"and has performed heat and tests on the main board " --- when testing for cracks and intermittants on a circuit board it is much more effective to squirt a freezing agent on the board. Lowering the temperature makes everything shrink and will open a hairline crack in the copper traces or a crack in a solder joint. Comes in an aerosol can from Radio shack or other service oriented suppliers. Just squirt it on while the board is under power.
Walt