Very nice work ! You have become an expert at the doors.

The connector probably has coke or something like that which has bonded it together. Kids used to spill their drinks etc, and the door / connector would rust as a result.

Thanks, I don't mind tidying up these doors. It always nice to open them up and have them operate smoothly as they should, same with the lock down bar assembly. I always do these with the doors. Nothing worse than that gritty feeling when trying to release the lock down bar.

Amazing transformation on the inside of the coin door, what did you use to clean it?

Nothing too special, I basically just strip the door back to its smallest components and re zinc whatever I can. Anything else I clean with scotch brite pads and the Dremel with a small wire brush attachment to get into any hard to reach area. All screws get de-greased and tumbled, the black ones then get re sprayed black again. The wires get cleaned with windex on a micro fibre cloth and all cable ties are replaced as I go. I pretty much just follow the same formula  with all of the under playfield assemblies too.
Speaking of cable ties, it is unbelievable how many you go through when cleaning looms and replacing them. When I did Flash Gordon I brought a pack of 100 and thought that would kill it! They didn't come close and I lost count of how many packs I went through. This time I just brought a big bag of 1000 to save me the repeated trips to Bunnings.