If you are using RCBS dies, is like I have here. I think the part that you are referring to is the decapping pin expander ball, or similar name. Maybe worth your while to measure the diameter of the one that works, versus the diameter of your initial one. As described above, your die body is going to smush the case neck too small diameter - then the expander ball is going to open it up, from inside, when withdrawn from case. Might find that your original is too big?? Can sand or file that one down fairly easily with drill press or lathe, or probably with care, a hand held drill. If that is your issue, maybe worth to try before spending money on another, that may be no different??