Quoted from jibmums:
I have a DE Simpsons and the right rear green habitrail VUK is working fine, but could use a bit more "oomph" in kicking the ball out. Currently I'd say half of the time the balls come back down and hit the edge of the lock hole, which is beating the shit out of the graphics at the edge of it. I've swapped coils with the other VUK, I've moved around the habitrail and VUK bracket to try to align them better, nothing else works, so I'd like to swap in the next-strongest coil. The current one is 090-5001-00, any idea what the next-strongest one would be? I have some Bally and Williams coils too, if any are compatible.
BTW, photo below is old, VUK was rebuilt with a kit from PBR.
I had this issue on Jurassic park. The thread I found had people suggesting a rebuild of all the components. Also, double check whether the switch is fully activating. The coil was no any ones issue and I doubt it is yours