New iPhone 6s - dip in back aluminium

Hi all,

Hoping for some perspective here.

When I press/use my iPhone 6s I sometimes get a slight 'creak' - which after thinking it's the 3D Touch screen that's poorly fitted, was in fact the Official Leather case moving in my hands against the phone back.

Removed case and the back of the phone has a slight dip or depression in it across the long edges, which was confirmed when I placed a metal straight-edge across the width of the phone. You can see light under the straight-edge. This means the case has a gap across the back of the phone which allowed movement of the case.

This makes me feel that the phone has suffered a manufacturing defect. It is 3 days old - shall I just take it back and get it swapped for a new one?

Checked my mates and they are straight as a die.... as it should be.

BTW - this was a new, replacement phone after I returned my first one due to faulty/buzzy speaker. Did they give me another pup from the same batch?

Not enjoying this phone as much as when I first got my 5s....