It has been my experience over the last 25 yrs or so that three things make what you describe happen. 1. dirty inside case necks have a smaller inside diameter. Take the time and run a brush in and out of them. 2. use Hornady one shot case lube and spray a bit directly inside the mouth. It won't contaminate the inside like oil will. 3 polish the expander ball. Chuck it in a drill and spin it on some 2,000 grit wet/dry sand paper followed by some polishing compound. If you do these three things I think your sticky expander ball issue will go away.