Answer to: case on the back of the screen is ungluedI also have the same problem with the same corner! A few MacBook Pro generations ago (titanium) I had the left hand side hinge break out of the screen. I suspect the hinge is broken out of the unibody and prying it open. See the hinge in Step 26 at this link. MacBook Pro 15" Unibody Teardown I think the left hand hinge goes because the right hand is usually used to close the screen and the screen twists, maybe misaligning and putting more force on the left hinge, breaking the mount. I haven't yet verified by removing the black hinge cover yet. I have been thinking of using epoxy, but would like to visually inspect the hinge first.