Do you have a new top rail installed? You may have not taken the washers out of the OEM rail and put them in the new top rail. This caused the 5 screws to protrude into the receiver and catch and lock the bolt back. Happened to me when I installed my Sidearmor Mod 3.
What was he saying that was a nuisance I remember watching his videos and I saw that he had an account on here that was banned. Or is he now "he-who-must-not-be-named"?
I've used it before and it works perfectly. It's especially nice that you don't have to wear gloves either. I've looked at the forums with the mold problems, but I personally don't think there's enough evidence to say it was the reason mold was growing.
I have a used Benelli M4 pistol grip stock for sale. Was only on my shotgun once when I fired it. Looks brand new and doesn't have any scratches or wear to it. Looking for offers.