Clicking in a certain gear with SRAM drive train I have a new bike with exactly the same problem and same drivetrain (SRAM GX) as shown in this video: 
                
             (not my video).
When pedalling with the chain on the 5th smallest cog, there is an irritating clicking sound. It is not loud enough to be heard on a busy road, but it is clearly audible when out in the quiet of nature. The cause is clearly visible in the video: one tooth on the 4th cog will pick up the chain and drop it back.
I live in a country where I do not speak the local language fluently, and I cannot get anywhere with the local shop. I gave up on trying to make the problem clear to them. I'm basically on my own.
What would you do?
Is it a good idea to just ignore the problem, and hope that it will go away once that tooth wears down? Will ignoring the problem cause damage (e.g. premature wear)? Should I try to push a warranty claim (I expect it not to be easy)?
It appears to be a rather common problem. There are many references to it online. The only suggested solutions I could find were to bend or grind that one tooth, neither of which am I ready to try.
The chain on a twelve gear cassette is very thin and the tolerances are close. Move the chain onto another ring and look directly at the cog as somebody turns the pedals. Look to see if the tooth is very slightly bent towards the larger ring by comparing to those next to it. Failing that, see if it is a machining fault, is the tooth chamfered in the same way as those around it. Note: some teeth are deliberately different to help the chain move across the cassette, but all should be slightly chamfered at the tip.