It's probably due to a mismatch between the shapes of your bullets and the business end of the seating ram. Many folks call Lee or whoever made the dies and get a spare seating ram, then coat a bullet in Pam or in Johnson's Paste Wax or some other mold release agent, and then fill the seating ram with JB Weld and set it on the bullet and wipe off the excess and just let it sit until it hardens, giving you a seating ram that matches the bullet shape.
I'll move this thread to the case bullet forum, where you may get more suggestions.