I have a Macbook Pro 15" Retina model with those annoying pentalobe security screws. This is my third replacement (first one had bad battery, second on had broken hinge). After a week of usage, something is very loose inside of the unit, and it feels quite large (like the battery isn't glued in, or a board is missing a screw, etc). I went to the Apple Store and had a "genius" look at it. He couldn't hear or feel the very obvious rattle. He took it into the back room, and apparently opened it and found nothing wrong, and had "15 of his associates" shake it and couldn't feel / hear the rattle. What's strange is that the looseness of the item increases as the unit heats up, leading me to think that it could be some of the glue that holds the battery in place. I'm at the point of returning the thing once again, but figured I'd take a look inside myself. I've fixed many a laptop in my time, but this is my first with security screws. I am just curious, does anyone know if opening this thing voids warranty? Additionally, if anyone has experience inside of one of these, any ideas of what to look for? I'm going to start by wiggling the batteries and go from there.