Hi, on third mac book pro now! Other two had screen issues, this one just over two weeks old and there is a heavy knocking noise, I noticed it when I turned it over to put in its bag, so gave it a slight shake (like you do!) with lid open and closed there is a nasty knock, sounds like something hitting the bottom panel, batteries??? Coming unstuck possibly. I have seen one other like this, genius appointment booked for Friday so will keep you updated!!