This has been a problem ever since the phone has came out, there are little tabs in the inside that come loose over time or that break when you take your phone apart. Mine are semi-loose but with a Silicone Cover on mine, I don't notice it at all.
To be honest, no. But that's because I take a lot of things I own apart. It's pretty simple if you don't mind voiding your warranty. I know there is some Youtube videos that will show you how to do it, it's relatively simple, just watch out for the little tabs on the side rails.
Mine became lose too. It annoys me because it makes noises when I put pressure on the sides. I put a piece of paper and it works out fine. Slide the back on and you'd never know it was even there.