I would reseat the connectors on the boards, especially from the backbox and check for any loose pins/wires, before doing anything more serious.

I don't think the display issue is related, but could be if it's poor connectors for all of them.

Obviously want to check/test the leaf switch at that hole, but symptoms suggest that's not it.

Left eject hole (I think that's what you mean, unless you're mixing up left/right: left side only has one eject, so a little thrown that you're qualifying it with "upper") is in the white-green row, I'd trace that carefully checking continuity.

I'd carefully check the coin door too: having accidental ground there can do weird stuff like that, and center coin switch is in that row. The fact that motion triggers spontaneous switches/scoring makes me suspicious something might be getting grounded.

Where does that wire go to? I couldn't tell in the video.

With it disconnected, I would check if there's continuity between coin door frame and grounding braid. I'm just wondering if that was someone's lazy way to repair a broken ground braid.

The other thing is, it still took motion to cause the problem. You should identify the exact contact happening, and then you can restore the ground properly.

IE. I'm wondering if you're just circumventing the actual problem by removing all grounding from the coin door.