Coils and flippers are designed for use without any lubrication. Why would anyone would ever recommend it. My aversion isn't about any extra dirt, but if it needs lube, there is something wrong with the parts. The issue will return when the lube runs out or the broken/worn parts get worse.

Replace the sleeve, they cost about 50 cents. If you don't have a spare or need it in a hurry, clean the original thoroughly and if it isn't worn you can reuse it.
Clean the plunger with a light use of scotch brite.
Check the pawl and assembly for wear.
Replace the playfield flipper bushing. These wear out and eventually cause flipper drag. Another 50 cents, but need a little care to reinstall.

Before you take things apart, manually move the flipper and observe the assembly to make sure nothing is catching or obvious. Sometimes they will catch on the EOS or on a loose wire, or are just worn in a way they move inconsistently.

But your problem is likely electrical as noted above. Misaligned or worn EOS switches are the culprit 90% of the time. EOS switches control the power a coil and could account for the symptoms you describe.

If you need more help, post some pics. There are also many threads on rebuilding flippers.

Shouldn't have come across that harsh, but saying Graphite is OK to a newbie on what appears to be his first repair, can sound like a recommendation since he asked about it.

My main point was to focus on a proper repair, not a band-aide.

Well I assumed this one was a Segasa-Sonic, not a Williams.

It is always the EOS, and as noted in several replies above, is the first thing to look at.

Based on the condition of that switch, you should rebuild those flippers, aas no one had touched those assemblies in a long, long time.