I wonder if the spring tension on the counter has weakened; thus you're getting erratic rotation? Maybe there is also accumulated dirt, dust, and other material, that is affecting the rotation? I have my 99 in pieces right now, because I'm re-furbishing it. AGI (American Gunsmithing Institute), has a great Dis-assembly/re-assembly DVD that shows how to take apart the counter, and how to re-wind it for proper tension, besides how to take the rifle all the way apart. it's an excellent video.

https://www.americangunsmith.com/app...99-Lever-Rifle

p.s. I don't advocate pirating DVD's.....but, you might be able to find a bit torrent that will let you see the video for free. again, I don't advocate it, but I'm just sayin'...

One other thing..... Try getting a can of Gun Scrubber, or something else that is designed to clean Gun actions, and take it outside and spray into the counter/follower area. If there is just some gunk there preventing the counter from operating correctly, this may be a quick fix. You maybe able to try using lighter fluid (the kind people use for Zippo lighters) also, since it's an old trick for dissolving gunk in gun actions, that also leaves behind a slight lubricant.

Good luck, let us know what happens.