I believe it has to do with the bullets being copper more than anything else; and that it is less malleable a metal than lead which I am used to using. I was able to fix it but I would say that it requires more attention than lead bullets for sure..
When putting in the first bullets I was attempting to figure out the overall length in order to make a fit into the chamber of my new rifle. The first two attempts were too long. So I put them back into the die and tried to shorten them. When I did that it was just close enough to the edge on one of the 3 grooves which are on the side of the bullet that it was stripping the copper. So I had to shorten them even more. I figured out an overall length that works but the general rule seems to be that any time I run them through the die more than once it seems as if this "loose" issue occurs. If you are even close to the edge of one of the grooves and it strips the bullet then you have to shorten or lengthen them more. When I was making minor adjustments to the overall length it seems as if it was more prone to this oddity.