Bad solider joint on the battery holder.
With the game off, put your DMM on DC volts and put the black lead on ground (the grounding strap or on one of the screws holding the CPU board in place). Put the red lead on each of the CPU board's POSITIVE battery terminal SOLDER POINTS. Test each of the three batteries' positive leads individually. You should get about 1.5, 3.0, or 4.5 volts at each
your game off and batteries installed, put your DDM on DC volts and put the black lead on the backbox ground strap. Then put the red lead on diode D2 on the CPU board. The banded side of the diode should show about .5 volts less than the non-banded side (which should be about 4.3 volts). If only one side of the diode shows voltage, this 1N4148 diode is bad.
Next test for voltage at the CPU U8 RAM chip. With the game off, you should get about 4.3 volts DC at pins 26, 27 or 28 of chip U8. If you don't, the battery voltage is not getting to the U8 RAM chip, and the game will boot up with the "Factory Settings Restored" error. Note pin 28 of the 28 pin U8 chip is in the same position as pin 1 of the chip, but on the opposite row of pins. Pin 1 is designated with an impressed "dot" right on the top of the chip.