Also got the following advise from Jim.
Inside the receiver is a firing pin block. Inside the block is a pair of back pins and a pair of firing pins with return springs around the firing pins. The firing pins can break or the back pins can break and the gun will fire perfectly several times and then barely strike the primer. This problem can drive you crazy. Look at the receiver and there is a big pin that is smaller on the other side. That pin holds the firing pin block in place. The firing pin block has another pin (after you remove the firing pin block) that allows the back pins and firing pins to be removed. It can get complicated to explain how to remove the top lever in a note and I won't try, but Kreighoff is your best bet.