Ugh, I came here hoping to read some good MMR drama. Just a simple adjustment problem though.
Here is your problem: The flipper coil has a nylon sleeve inside of it (which has the flipper plunger moving inside of it) which extends out from the coil and just barely through the bracket that holds the coil in place. Your bracket (or perhaps the other end, the coil stop bracket) is loose/misaligned such that your sleeve is not going through the bracket, which means your flipper plunger is rubbing and catching against the bracket each time it moves instead of smoothly through the end of the sleeve. The sleeve will only extend through the bracket (barely) if the coil is firmly sandwhiched between the two brackets, as on your other flipper assembly.
The end bracket is held in place with 2 Philips screws. Loosen those screws, then see if you can reposition it closer towards the coil, then re-tighten firmly. If not, loosen the bracket on the other side of the coil (should be 2 Allen head screws) and see if you can push it in more towards the coil.