I killed one. Left power applied too long when I learned that all my flashers lit up and many coils locked on. Thinking over what repair work I was doing at the time and found out I plugged in my game ROM backwards on STTNG. I had installed the game ROM in the MPU board I was testing out after repairing and had the board turned upside down and didn't double check myself before turning on power. ugghh..

So I can see that is possible having random things happen at start up in your case.

Please post a picture of the display issue.

With power off, reseat all ribbon cable connections.

If that does not help, do a factory reset/restore.