I have a second hand rem 870 express the previous owner lent the shogun to a friend that somehow managed to jam up the action so bad he tried to reassemble it using a hammer. The original owner sold it to me cheap and I disassembled it and was able to get it functioning again. Since I'd only ever fired it a few times after it was fixed I hadn't noticed the safety doesn't properly engage. After cocking then engaging the safety and pulling the trigger it holds then on the second pull the hammer falls. (Of course I only tested this with an empty chamber and pointed in safe direction.) does anyone have a suggestion on repairs or what the problem could be?