WD-40 isn't a long term lubricant. It is flammable right after you spray it (great around sparks from switches if you hit the stoichiometric ratio correct). It then attracts dirt and dust. Next it all turns into a gummy substance. At this point it isn't just not lubricating, it is making the issue worse by restricting movement. Finally if left alone it will turn into a solid mass like a varnish. you tend to see this in EMs where things needed a bit of work, but someone "fixed" it with WD-40. The game might work for a bit, and then it will be worse.

Look, as far as pinball machines, WD-40 is awesome for pulling out rusted leg levelers that are being replaced. A shot on that, and let it sit. But don't use it as a lubricant.

(I know, way off topic, but it was asked)