Clicking in a certain gear with SRAM drive train
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.