It definitely was a bad MPU. I didn’t attempt any repairs on it since I was able to get a refund from the seller I purchased it from. I bought another and now the machine has no tilts.
I still can’t get the spin and play 3 coins buttons to work, but I’m going to work on the some more soon.
I’m still going to attempt to fix the bad MPU that’s not seeing the door closed, though. If I ever get that one working I’ll post an update.