Help with "rattley" Happ trackball

[QuixoteQuest]

Got a new USB/PS2 3" Happ trackball for Christmas (in a new cabinet). It was a little tight at first, but has broken in to be quite smooth and enjoyable. However, recently it started feeling a bit "rattley" in the hand. It's hard to describe, but it just doesn't feel or sound the same. It seems to function fine. But the feel seems a little "off" and it sounds noisier when spun. It had a little oily-dust-gunk like any ball mouse would get, but even when cleaned off it still feels the same.

Anyone understand what I'm describing? Is this a normal issue or is there something I need to clean? Any disassembly requred?

[ChicagoDave]

I had this problem happen after the kids had some pizza.  They didn't wash their hands and started playing with their greasy little paws.

It was the grease on the trackball that was making the noise.  I wiped it down using a paper towel with some Windex on it and it solved the problem.

[BobA]

If you do not get satisfactory operation after external cleaning you might want to see that the rollers are clean as well.

[northerngames]

give each bearing a fling and it should spin for a few seconds if it is slow and stops rather fast the bearing is going bad I just tested mine and found one to be bad.