When you take the gun apart, check the shell latches. These are the strips of metal crimped into the inner sides of the receiver. There are two and they oppose each other. They are the pieces that you have to press in to get the guts of the shotgun back into the receiver when you assemble the shotgun. They are only crimped into place. They can move fore and back and cause problems, such as making it difficult to move to forend slide.