Don't F*ing do that.
If the plunger seems to be dragging in the coil sleeve. Easy fix.
Turn game off. Remove balls ( game, not yours ) lift playfield up and lean on backbox.
Unhook coil connector. Remove bolt holding troll carriage to plunger. Remove two brackets/four screws holding coil/plunger on.
Now that you have the coil and plunger out. Remember the order of the parts, coil, brackets, coil sleeve, etc.
The plunger is two piece, held together by a roll pin. That roll pin is sticking out a bit. Pound it back in. File the area smooth. Check if coil sleeve is cracked or broken.
Reassemble. Done. Miller time.
LTG : )