Quoted from D-Gottlieb:
The small ramp behind the garage door leading to the upper playfield is very prone to breakage. Check for cabinet wear around the buttons, worn out itchy and sratchy hole and the shooter lane.
Just to add to this point, yes these are all common wear areas, but there are easy ways to fix (or at least conceal & protect) these areas if the damage is mainly cosmetic, so don't let these issues deter you from buying a game if that is all that's wrong with it. It's a great game, so many of them spent a loooong time on route.