Byrdguy,
It is quite possible that new piece just needed a little break in. Although it is not common with Glocks,it does occur.

I bet now it will chug right along no matter what you put in it.

If the problem does still exist,don't take it back to the dealer but give Glock a call in GA. They will probably send you a shipping label. Trust me on this,a gun in for repair does not stay long at the plant. Turn around is probably a week door to door.

Wayne