I haven't used my original upper in my Powder Springs MAC-10/45 in years since putting Lage goodies on it. Until today, that is. With the original upper and bolt installed, pulling the trigger releases the bolt as normal, but the firing pin apparently doesn't even touch the primer. The gun is cleaned and oiled. Is there something than may have fallen off the bolt after years of storage? Any good videos or instructions on disassembly, inspection, and reassembly of the original bolt? It works fine with my Lage upper installed.