Presses take time and lots of practice to get the hang of.
Best suggestion is to make a "template" bead out of playdoh or something similar. Use that as your guide for how big to make the initial bead and before long you'll be making uniform sized beads that will always come out well pressed.
If your bead release is breaking off you've either coated your mandrel too much or you're pressing too hard
Unfortunately it's probably going to take you more than one session to get the hang of the presses but keep at it. It's worth it
-Yee
(who is a total press ho)