Quoted from currieddog:Try this: disassemble and clean plungers and coil sleeves with 91# rubbing alcohol and swabs. Then sand plungers with 600 grit sandpaper. Put a spritz of powdered graphite in sleeves before re-assembling.
I would skip the graphite, not needed and messy. Take your time, order and wait for parts- it will be worth the wait.
Follow this guide-
https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers