When I get an expander ball that acts this way I will remove the rod and ball and put it in the lathe, substitute hand drill or drill press and polish the ball with 800 to 1000 grit paper. As soon as it is polished to a mirror stop. You do not want it undersized just polished. This normally fixes the problem. Also note that as the case is used the neck will become work hardened. Some cases do this faster than others, 5.56 / .223 are the worst. If the ball is very hard to pull back through it is probably time to anneal the case necks. I do them in lots, every 4th to 5th loading for 06 class cases, every 3rd for 5.56 class cases.