Wow - you are really having a tough time!
There is no excuse for the sling swivel to break - that's pure crap. Of course, every one I have installed myself has broken!, but not out of the box.
That noise you hear is the inertia spring aka the spring that makes the gun work.
Click on Benelli above, then Innovations, then Inertia Recoil Design. You can read all about the design there.
Sounds like the black gun was badly broken or missing parts.
I have put 30,000+ rounds through Benelli semis, and the only malfunction that has ever caused me to take the gun apart was; dry firing, putting the safety back on, and then pulling the bolt back with the safety engaged. That locked the gun up good!
mudhen - CA