If the mold is dropping that narrow I can think of a few things.
1 Worst case thinking is zinc contamination. This would cause the alloy to not fill the mold.
2 Mold not hot enough. Are there wrinkles or lines in the nose, and base. This can be remedied by preheating the mold.
3 Defective mold. If so call Lee thier customer sevice will fix the problem.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.