My biggest preve is buying a pin and discovering/believing a part or item is missing. I mean engineered missing, not just removed by a previous owner. An example is my Maverick. Near the flippers, the lane g.i. On both sides there is one bulb and then space for another bulb. There is even holes in the plastic lane for the bulb and a circle on the playfield for the location of it, just no hole was drilled. Drives me crazy evry time I look at it. I have other examples too but you get what I am saying I hope.
I guess Stern is not the only company that did/does cost cutting. Data East/Sega did it too.