Quoted from livetowin:
Yes, pressing the left flipper button only flips the bottom left. Right button flips both right flippers. Pushing in left and holding it in and then pressing right makes the top left one flip. Weird is right haha
It does not sound like it is wired correctly.
You will have a blue/white wire that goes to all flippers.
And then you should have an green wire that goes from the lower left flipper to the upper left flipper.
And you also should have a orange wire that goes from the lower right flipper and up to the upper right flipper.
Caution: I am guessing on the upper flippers in chance that Lightning flippers might be wires like Seawitch. The drawing for Lightning does not show the upper flippers. This needs more research as it is possible Lighting drawing were put out with bad info. as some other Stern drawings.
Here is the Lightning drawing for switches and solenoids.