Galaga control and credit problems

Hi,
I have a galaga board that works some times and other times it Starts
by its self into 2 player mode. Then you can sometimes move the ship
but mostly not, or even shoot.

If you can start the game in a one player game it will all of a sudden
jump into a 2 player game and you keep hearing the credit sound going
over, and over and over very fast.

This board set does it in a few other cabinets also so not just in one
cabinet either.

Any pointers on what to start with. I have a pdf of the schematics but
it is blurry. Could it be a buffer or one of the resistor packs?

plus all the resistor packs donot test out to the value on the pack,
as in some 1ks= 900 ohms - 300 ohms, and the 2200 ohms= 1.5k- 3k
ohms. they are in circuit but that should not make a diff right?

Please let me know as I am dying to get this going and play Galaga .
thanks
Jay