I think I would have hammer seated the caps since pushing on the caps with the hammer seats them real well.(gently rest the hammer on the cap and use your thumb to push the hammer to seat the cap.
If you watch then you'll see if the cap moves and that will tell ya if the caps are seated fully or not) Point down range when ya do it though.
After your're sure the caps are fully seated and that variable is out of the way then you can test other possible causes for the anomaly.
I bet your caps just aren't seating all the way since you probably aren't using anything to seat them. A wood dowell can be used. Or a brass rod or a fiber glass rod or ect. ect. Since the hammer is there already you may as well use it at first to see if the caps are fully seated when you first put them on and push a little with your finger.
I'd rather use the hammer to seat caps since the cap can go off when it's seated on rare occasions. It hurts if you're pushing on a cap with a finger and it ignites with a load in the chamber.
After you have determined if the caps are seating or not then the next thing is to come on here to get the next step in the scrutinizing proceedure.