Mine does this....cuz like it's been said here.....it's dirty. If you press down on it and scroll it around and almost abuse it (lol) it will usually correct itself. Mine always does.
Is there a way to make my track ball stop jamming up beside just cleaning it?.
1) Keep your hands clean
2) Keep the device in a protective shield
3) Don't ever put it in your pocket unprotected
4) Keep the device clean
5) Keep the device out of dirty or dusty environments