Eko - Would a worn stylus account for the bad tracking? It actually still sounds very nice.
Well, because there are so many other variables, it's impossible to say whether a worn stylus is causing your problem. But, given my experience with the OC9, it's the most likely scenario. The only way to know for sure is to get it under a microscope at a knowledgeable cartridge dealer. If it bothered you enough to post this thread, I think it's worth the time to send the cartridge out for inspection just to satisfy your curiosity as to where you stand on the wear curve.
I disagree with Tfkaudio in one important respect. He may well be right that your cartridge has some life left. But cartridges are easily replaceable. Records aren't. If it were a $5000 cartridge, I might be more inclined to suggest you squeeze every drop of life from it but given how inexpensive the OC9 is, I say better safe than sorry.