Hi. I have new macbook pro 15 retina mid 2014 and i notice that when i lift it today and removed my hands under the macbook it came a kind of cracknoice/nock noice, only one sound every time my hand slides over the aluminum cover under the macbook, just like the aluminium plate under moves or something? Anyone that have notice this before? It is a nock sound when it happens. Thanks for reply.