The tiny roller gets stuff on it from fingers, and from the keyboard, then the mechanical
control bits inside the mouse the tiny roller ball rubs on, gets stuff on them, too. The
answer has been to try another finger or one on the other hand, initially; that's only a
temporary fix. The answer is to clean the roller. This can be done without disassembly.
My roller ball wired Apple Mouse (also known as Mighty Mouse for a time) and wireless
both share a similar internal device that gets gunky. The symptoms for both are the same.
Re: How to clean an (old, weary) mouse -- note suggestions and comments in the
linked article on how to clean (sounds like taxidermy) methods; since the comments
also include non-invasive cleaning methods; as I mentioned and also tried successfully.
It is a easier to get a spare clean good used similar Apple mouse (USB) from macsales
or other vendor so you have two; and clean them alternately. I clean my Apple mighty
mouse a few times a month. Helps to extend the period between cleanings by use of
they keyboard up/down arrows; and locate buttons for Home and End of page.
Hopefully this helps with your patience, to know it is possible to make it work again.
There had been other methods of cleaning the mouse without taking it apart, those
web sites no longer exist; so their archived wisdom appears to be lost on us...
I've gotten quite a bit of use from my 50¢ investment in a nice condition Apple scroll mouse.
Mine did not need the roller cleaned, on first try it worked OK. The outside was dirty, though.
Expect to pay more than 50¢ for a mighty mouse USB, from macsales, though.
Good luck & happy computing! 🙂