I have the exact same issue. Went to Apple Store on Tuesday where they reseated my display and the problem went from intermittent and not too bad to constant and may be 2 or 3 times worse so tonight I went back ... As they told me I should on Tuesday if I had any more problems.
Now I'm in the situation that I have to try taking the phone back to Carphone Warwhouse instead as Apple will not accept that this clicking is a fault. They even documented it for me to show CPW. But they say 'it's due to how the phone is made' that the screen clicks. I say it's faulty becuase they don't all do it.
It's total BS. I have bought every iPhone they have made up to getting 6+ in December. I will think hard before buying any more Apple products.
The option for a 1 time exchange was presented but I declined and am going to fight them on this as far as I can until they fix my phone. Or they can give me money back. They have to accept that these phones are faulty.