It's happened twice that it can't focus (unless the thing I'm taking a picture of is ~1cm away from the lens).
The camera 'knows' it's not in focus, you get a red square (unless the thing I'm taking a picture of is ~1cm away from the lens, when I get a green square).
Focus problem exists with stock and FX Zoom app and after clearing camera's cache and data.
I've seen online a couple of people reporting this problem.
I can return it under warranty, but would rather not 'cos I'll lose my slightly expensive screen protector and will be without my phone for a bit.