Quoted from Tranquilize:
While this bandaid may work, it is not the correct solution. Your flippers should barely need springs at all. If the spring is not pulling it down, you should find the cause of the unwanted friction. Friction wears on parts quickly. Fix it correctly and be done with it!
It would be highly unlikely in such a new game to have issues with the plunger or sleeve for wear unless it was assembled incorrectly.
I’ve had to replace two springs on a friends Guardians. One just snapped in the middle which was bizarre. The other side was a off in its size and appeared to have reduced elasticity. (The left flipper return to rest was lethargic) Maybe, it was a shitty batch from their vendor or just the wrong ones. Who knows? However, the spring is something that is to be looked at and thought about as perhaps a problem and not a band-aid fix or a incorrect solution.