I received The Panasonic 12 – 35 F2.8 lens today and I think My copy is defective. In my hand, before I mount the lens it makes a Very discernible rattling noise as i turn it for inspection.I own several other Panasonic lenses Including the 100 – 300, The Pana Leica 25 mm, The 14 – 42 kit, and the 14 f2.5 and have not heard a rattling noise like this. Is this the OIS Or is this unusual for the lens? The lens also had a lot of ingrained dust in the grooves of the body so I am suspecting that this lens has been used. For a lens this expensive I was expecting it to Feel and sound more solidly built. What do you think? Input from other Owners would be greatly appreciated.