game maker vertical roll (cpu probs)

[azgamingslots]

this one has left me pulling my hair out

bally game maker: crt monitor has a tiny bit of interference on screen and picture slowly rolls like someone has played with the vertical hold button on the monitor, 
however adjusting the monitor wont fix the problem, monitor recently recapped, works fine in another gm, the problem is in the cpu board.

(problem followed board when i swapped into a working game maker)

already replaced main, graphics and game chips, most of the removable chips on the board, rfi capacitor on upper right of board and the problem is still there.

anyone else come across this problem and or know how to fix?