Same thing happened to me on my progressive loader. I have loaded for 25 years and never a quib load but one day I was shooting my .45 ACp and the slide didn't come back and it felt weird. I racked the slide and released the mag from the 1911 and sure enough a bullet was stuck in the barrel. I tapped it out with my brass rod and started to fire again. I think I went 10 more rounds and then the same thing happened. Well that was it for the day for the 1911 and so I started to shoot the .44 mag real slowly. About 5 cylinders full and the same thing happened. I put away my stuff and headed home. I couldn't figure out why I would have squib loads. So the remaining loaded shells I put aside with a note on the outside to check for squibs latter on. I reloaded and watched every case as it was going thru the reloader and I got into about the 10th round and sure enough no powder. I took the powder measure apart and it was fine, now I am really confused. While I am pouring the powder back into the hopper from the container I notice something flash by my view and into the hopper. I got a gallon pail and dump the powder out of the hopper again and into the pail. Sure enough in the bottom of the pail is a small pistol primer. How the heck it got there I will never know but once in a while it would plug the hole up and no powder would come out and thus the squib load. Now I pour all my powder thru a strainer first and then into the hopper and I watch every case as it goes by. I am extremely careful now and if I had more money I would upgrade to a progressive that has a low powder die spot on the turret, but that will have to wait. When I got time I looked at the reloaded rounds that were in question and about 1 in 5 were squibs so I dissembled all of them.