I need some help here. I have a m&p 15-22 sbr with thousands of round through it. I just started having this issue. When I shoot the gun fires, round ejects and loads a new trigger but when you pull the trigger the trigger is dead. The hammer is up. When I extract the round in chamber I can see a light fire pin marks on the rim of the case. Anyone have an idea *** is going on and how to fix it?