My new iphone 5 loses focus as soon as click on the camera button

I have a brand new iphone 5 and it has a focu sissue. The other day I was taking a picture of an object that was 50 or so feet away, I focused on the object by tapping on the screen and as soon as I clicked the camera button to take the picture, the focus changed and ended up taking a picture of the surroundings rather than the focused object. Initially, I thought my hand was sahking but then I had my wfie try it. The same problem. I tried on my son's iphone 4s the same way and it did not have this issue. Finally, I reset the phone (using home button and the power button) and the issue went away. Unfortunately it came back again today. Has any experienced this issue and if so, how did you solve it?