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!

Quoted from imharrow:

Do not assume it was correctly assembled. I know someone who spent weeks trying to track down an issue with stern. Eventually brought it back to their distributor to debug. In the end it was a complete catastrophic failure of the coil stop. Rivot completely failed and the stop was detached inside the coil. Destroyed the entire assembly.
They never took it apart because it was brand new, no plays when the problem started. I recommend assuming everything is faulty until it can be shown to be correct.

Quoted from Tranquilize:

If we're arguing that the spring is defective or the incorrect size, then yes, the spring should be replaced. From what I understood, the fix posed was to replace a correct spring with a stronger spring. As for the sleeve and plunger, sometimes even a slight angle in the way a screw was screwed into the PF can cause the direction of the plunger to be off, hence causing friction. You'd see this in the sleeve right away. On a new game, the wear would be minimal, but with a bright light, you'd see it. I'm only suggesting that a close check for friction has fixed this type of flipper issue for me 100% of the time with a working spring. I'd guess that I've come across the issue about 20 times or so.