YOu know, on the Performande Brand cats anyways, Nacra, etc., I would usually replaced the plastic ball every season or so, and use locktite on the threads when I installed a new one. It was always easy enough to get back off, WHEN you wanted to replace it.
Also, I agree with whoever stated that, you have to make sure it's threaded on all the way, so the weight of the stick doesn't strip the threads out, then, when rigging, de rigging, it's very likely to pop off.
The balls are pretty cheap, replace every season or so,
thread it all the way on, and it won't pop off.