Ok, 3/4 of the way up, that's our diagnostic clue.
On Forster dies, if the expander ball is not down far enough, you can experience the condition you are experiencing.
They this:
1. Run the expander ball stem all the way in.
2. Run the ram as far as you can.
3. Screw the exander ball up to where it just below the neck inside the case. It will take some adjustment, and feeling the interaction between the case new and the expander ball to find the optimum position for it.
Here's a picture to help envision how the Forster dies are different from common dies.
The expander ball sits high in the neck, and if it's not down far enough, there isn't enough room for the neck to clear it in the upper portion of the die: