Quoted from Homepin:These machines are 20+++ years old.
If I was having strange problems like you are I would replace all of the ribbon cables before doing much more.
Remember, these connectors were never designed for multiple insertions, sometimes as few as 100 cycles are specified for some of the connectors used in pinball. This would make almost all of them past their use by date well and truly.
A lot of connectors are only good for 25 insertions.