Quoted from Pimp77:
Mine doesn't either. You likely have a worn x-nut that is making the whole mechanism
sag. This puts the glove closer to the matrix and more likely to pick up a second ball. Replace that nut!
I tried this fix with my JM and it didn't work, unfortunately. In my research, it seemed that picking up multiple balls was a common problem on JM. Never found a fix before selling it. Tried everything.