My case is creaky on the edges and it's a XS case on a XS. Apparently taking the case off to clean your phone stretches it enough to where it loses its snugness.
I have noticed that aswell. Before I got the saddle brown case for my Xs, I did have few other colours and some of them did creak a bit.
Not sure if some of them are a bit more snug or they stretch over time due to regular removal of the case.