After inspecting mine, I might see a possible way it could fail. The common (not really ground) is the entire stamped metal tower, which has folded contacts from the base to the tower, from the top of the tower to the top metal plate. and then again to both the coil and the light fixture. So one side is proper wire- in fact individual wires for both the coil and another for the light, however, the return path is through folded metal tab connections that are painted.
So yes, quite a few places this could go wrong.
The white covered wire is the coil wire, the black wire also to the same terminal is the light.
The other side has no wires, and it basically making connection to the red metal stamped baseplate. That in turn must make connection to the silver painted tower folded tabs.
Then at the top, we have the same problem, the tower silver folded tabs touch the red painted metal top plate, and then the black metal folded tabs are making that other side of the connection to the red metal plate.
