With power off, remove the plug on the display, then reinstall it. Power up, then report back on whether the issue cleared.

I assume you know how to get into the back box. If not, we can walk you thru it.

While in the back box, look for AA batteries on the circuit board in the upper left side. For now, I just want to know if your machine has them, which would mean the MPU is original.

Also, try switching it to another spot, such as player 4, and see if the problem follows the display.

This will tell you if it is a problem with the display, the harness, or the MPU.

It sounds like you have a connector issue and an original battery. (I had a brain cramp in my earlier post - Williams machines of that era use 3 AA batteries)

Has the battery started to leak? You said hard wired, I assume the leads are soldered to the board. Regardless, you need to get that off of the board before it leaks and destroys the circuit board. There are several options available, the easiest is to install NVRam and remove the battery.

(The battery is used for saving how much per game, number of balls, points needed for winning a game, and other game settings.)

Since we know the display is good and the position acts the same, With power off, unplug J1 on the MPU And plug it back in. Power up and see if that fixes it. If so, then that connector should be repinned. If this fixes it, you may be ok for awhile, but the issue will come back. Over time, these pins corrode or lose their spring tension, resulting in poor connections. It’s also possible you have bad connections at the display unit, but in my experience, most of the issues with connectors are on the circuit boards in the head. Another possibility is cold solder joints on the MPU, which requires reflowing the solder, but go one step at a time.

The ram chip should be socketed, so changing it out should be easy. Note the indent on the chip - that indicates where pin #1 is. You pry up on the chip, evenly, on each end. Kind of rock it out. Once out, you install the NVram by slowly pushing it back into the existing socket. This is best done with the board out of the machine so that you can see that the legs of the chip are lined up and going into the socket. You don't want a leg to miss a socket hole and bend up.

While the board is out, clip the leads of the battery to get it out. The main thing is to remove the battery body. Once this is all done, after reinstalling the MPU, you will have to reset all of the parameters such as coins, score thresholds, etc.

Pinitech is a good source for NVRAM. The website also shows where the NVRAM gets installed. I just looked, and everyone is having supply issues - they are out of stock everywhere, so you will have to keep your battery on the board. Keep a close eye on it - if it starts to leak, get it off and wait for supply to replenish. Better to wait than to destroy a board.

I'm hoping others will chime in with ideas about the credit issue.

Correct.