unfortunately most new MacBook Pros also have this issue.(2015,2016 and 2017)Actually.. now that I tried again I can feel something moving inside. When I listen really closely I can hear something ticking real softly.
EDIT: You know what, I will return my MacBook since I'm still in my 14 day return period. I don't want to risk this thing getting damaged over time by this issue. Will probably get a MacBook Pro instead.
see this thread:
https://forums.macrumors.com/thread...have-that-rattle.2052250/page-3#post-24763863
that being said, it's unlikely to cause any harm.as it's the plastic sheet (called light guide) inside the display that is poorly secured and badly designed become detached from glue tape.so it won't damage anything, but it's surely annoying and frustrating, in some machines like mine it's very loud and easily noticeable.