I SMELL A BIG FAT DIRTY RAT!!!!!
So you use 1 machine as a parts machine, but then to sell on you install a whole WMS relay board???
...NAAAAAAAAH,
My guess also is that this is how it should be... quick check on some schematics would verify this.
Im thinking that this repairer wanted you to put this game into the old "too hard basket" and sell on for say $100? Double your money??? Cant be bad eh?
LOL