I'm bumping this topic because I just discovered the same issue from VUK kits I ordered from Mad Amusements. I've come to the conclusion that none of these online parts dealers realize the plunger's pinhole is simply too small for the metal pin they provide. Thankfully I didn't need the plunger part from the kit, but I can see it being very frustrating for those that do need the entire kit to work. Comparing my original parts to the rebuild kits, the pinhole is noticeably larger on the original plunger assembly. The only way I can see to correct the issue is to get a properly sized drill bit and drill out the pinhole to make it the correct size. You cannot force the pin in, so this must be done.

Just posting an update in that my idea of using a 3/32 drill bit worked perfectly to correct the hole size on the plungers (which were incorrectly sized at 5/64). It only took a few seconds to make the modification, and now the pins fit properly as they should.

Just a heads up for those thinking about buying VUK rebuild kits for their old DE/Sega/Stern what have you projects.

Well the point is you shouldn't have to buy something like that. Clearly the parts manufacturer was in error here by setting the locking pin hole at 5/64 instead of 3/32.

The rebuild kit comes with the pin.