Sorry, never happened to me on my LOTR. And I'm also terrible / learning in the pin repair dept.

That doesn't sound good at all. At first it sounded like a grounding issue, but if your display showed the "press start" display, you might check out your boards. Make sure those batteries didn't start leaking on the boards. You might also want to push down on all the chips, like ROM chips and what not to make sure they're making good connections.

Can't see a GI fuse causing that, but I've been wrong before. If it happens again take note of where all the balls are when it happens: in trough, ball lock, etc. Sounds like a classic switch matrix problem.

I agree bet the problem shows back up.

If it crops up again, I would start with what LilRocky mentioned. Check the boards for battery acid and make sure the chips and connectors are pushed in firm.

Until this problem reappear you could look into the build in switch test in the diagnostic menu. That can be a usefull tool when you have switch problems.

In the first part of your description it sounds like a switch activates only from the vibration in the game, but i am not sure it would make things get mixed up like showing 'press start' on the DMD sporadically.

I would look into the four switches (33,34,35,36) on the path of the death. Use the diagnostic tool to test if they work normally.