I think I mentioned the overloading issue. Sorry, if I confused anyone, my intent was only to suggest and make sure you did not have an extra round jammed in, as this would be an obvious fix. My suggestions are based on diagnosis of issues to elmiinate and narrow the culprit.
Rob - I concur, it is definitely a good idea to let you see and fix if anything is out of spec and requires adjustment, especially, machining, or warranty, if it is available.