Well that didn't take long. Sigh. Player came up to me tonight and said BTTF froze when he got a replay. Sure enough, the ball was stuck in the VUK and the game was frozen with "Replay" on the display. Cycled power and it seemed to be ok but soon discovered that even with only one credit on the game, when it's over, it asks you to enter initials for 4 players, regardless of the P1 score and despite that you only started a 1 player game, and awards you 12 credits. If you play through another game, the issue repeats and then it's got 26 credits. The machine has a brand new Rottendog MPU with NVRam. Any ideas? This is a new one for me. I've re-seated everything that can be re-seated. No change. Stumped on this one. Just got done restoring this machine not more than a week ago. Been on the floor for 6 days. Frustrating. Here's a video for illustration...

I found the issue. It’s an issue with the NVRAM. If I disable the High Score save option, the game ends like normal. If I enable it, it asks for 4 players worth of initials on a 1 player game and adds 12 credits.

If I remove the NVRAM chip and restore the High Score save option, the problem goes away but I get a “memory error, open coin door” error, which is understandable. I just acknowledge it and proceed. It’s something with the NVRAM chip. We can make it work for now but people won’t be able to enter their initials.

Replying to this to update that a new NVRAM chip has officially fixed the issue.