This little Shimano Sahara 1500 is probably 10 years old or so but I've taken care of it with a cleaning/lube/oil every year or two and it's been a nice little reel for fishing small streams. Recently I did a quick wipedown of the exterior, put a drop of oil on the bearings where the handle slides thru and put a little grease on the spool shaft where it goes down into the body. I didn't bother opening the case to put any grease on the main gear. Reel was working smooth and flawlessly before I did this.

 

Today I use it for the first time since the lube job and I can feel a little click or whatever during the retrieve. I R&R the spool and it still does it. I watch and I see the spool does a short herky stutter every couple rotations - like a quick back and forth stutter even though I'm turning the handle forward.

 

Any suggestions to correct? I love to buy new reels but also like to keep em running, especially when they have served me so well.

Hard to say.  But I'd tear it down, give a good clean and relube, and try again.  My guess is the grease caught some junk that was already in the reel and migrated it to the gearing.  But who knows.