When the puck was new, there were many modifications for it that would allow it to become a "normal" mouse. These were usually little covers that would slip over the mouse itself to make it similar to a generic PC mouse in shape.
I've only had problems with one puck. It was at the Goodwill Computer Works center I work at and I am going to make a safe bet this one came from a middle school. Not only did it not track well at all, the purple part of it was covered in that glitter makeup that all the 13-14 year old girls seem to wear.
I've had only a few other mouse problems in my life. I've had a ProMouse short on me and had a Compaq mouse stop tracking well--probably because its former owner was a Solitare addict. Well, there were the dozens of missing balls I've seen, but that happens in a school.