Are we talking about the 2016 model or the 2017 one?
It happens on both. 2016 and 2017, 13" and 15". It tends to be isolated to the left side of the keyboard and the upper right because the heat makes it more obvious.
The butterfly mechanism for the keys is incredibly small, and the tolerances are virtually impossible to maintain across the entire keyboard to create "perfect" keys. I've yet to see a single new MacBook Pro that DOESN'T have this issue on at least one key.
The good news is that, in almost all cases (and I tend to actually think it is all cases, it's just a matter of time) the issue will eventually resolve itself. The mechanical parts wear enough where they stop sticking and thus clicking. It's worse when the machine is warm because the keys expand a little, which can cause sticking. Fortunately, they are springy enough that the stick doesn't actually impact the feel or function, it just creates a strange sound.
It's silly to return a machine over this issue. After a few months, if you actually use it instead of look at it, it will go away. The only way to fix the issue completely is probably to redesign the mechanism or use different, softer, materials.