What you describe does not soundlike a bad bearing. It sounds like a poor quality contact between the cartridge pins and the leads. If you can clean and gently dis-connect and gently re-connect the leads to the cartridge pins I think you may find some improvement. Or the cart is just bad and worn out. Try the leads and also while your at it if you can replace the RCA jacks or clean them too. Which phono stage do you use?