How do you notice the movement, does it just happen naturally or simply when you press down on the buttons?
I've been reading up on this a good bit, and someone on the androidcentral forums mentioned a sort of fix using a tiny bit of black caulk you can find at a hardware store to cover the light leakage, however, first of all, we should not have to resort to such methods, and second of all, if this is mostly an issue with the screen not being sealed correctly, it would not fix that.
Honestly, you can never expect to have a perfect phone, but this seems like a bad oversight imo. If it was just light leakage, that could be considered nitpicking, but the screen not being on properly? What worries me most is any future problems, such as increased light leakage, dust getting beneath the screen more easily than it should, and possibly the screen becoming more loose over time.
The worst part about this is that it has made my phone feel more like a rental....sure I can customize it and all, but most of that stuff will be gone when I get new one.