Had a Bally Eight Ball with an Alltek mpu and sometimes the game would get all weird with crazy displays, sometimes it wouldn’t boot. Whenever it would malfunction the red lite on the mpu would lite up. Fixed it by recrimping a couple wires on one of the connectors, either the top left or bottom left of the mpu. I think it was a red wire on top left. Try wiggling those connectors with the game on, see what happens.