Just one thing to consider and something that created one of the so called "lag" of previous Galaxy versions, the Home button is used to open the camera with 2 quick press, before it was used to open the S voice with the same, so obviously when you pressed the button once it had a "lag" (that I'd call it more like a delay) to see if you were trying to press home once to go Home or waiting for the second press to open the S Voice.
So what I'm saying is that even when mine doesn't seem to be doing what you describe, it may be possible that the speed in which you are doing it may be causing the phone to wait to see if you are going to press again so it can open the camera, again, I'm just guessing here, but I can advise you to press the home button with a one firm motion and see if that can help, if not, don't let your 14 days expire and go get a replacement.