Check the fish paper insulating the red replay button from the switch mounted behind it on the door, I'd double up on that fish paper.

Is that yellow wiring a coin drop simulator/doorbell mod? Look closely at that modded coin switch on the door, make sure the switch leaves are insulated with fish paper as well.

Unplug the door jones plug and use a meter to check for shorts from any of the jones plug pins to the door metal.

I'd assume the replay button and coin switches are at line voltage - they are in a 1965 Bank-A-Ball.

You still may want to consider a new line cord with either a polarized 2 prong plug or a 3 prong grounded plug.

https://pinside.com/pinball/forum/topic/replacing-line-cords-plugs-wall-sockets-vids-guide