Need Help Ms. Pacman is disappearing

[razor1]

I have an original unmodified Ms. Pacman Upright with original PCB etc. When the game boots up, the welcome screen apears and technically you can play the game, but all the ghosts and MS. Pacman disappear and reappear. There is a vertical line that runs from right to left and when it hits the character it appears for a second until the line moves and then they disappear. Any ideas? I already tested all secondary cards on another machine and they work flawlessly. I also swapped out the 5E and 5F chips and they're fine as well.

Your help is much appreciated. Thanks.