It is not related to overall movement of the chair, rather than the person sitting on it. Simply put it feels like the overall weight shift somehow causes this. Not the minimal movement in chair. It might be the lumbar support because I feel it more on the back towards the bottom than anywhere else. This is also probably why we can't replicate it, we may need someone sitting on it and, and then again, it is very difficult to simulate driving conditions naturally.

If any one of us got someone we trust enough to let them drive freely and make turns and accelerations while we go down in back seat and try to pinpoint it, this may be the only way because nobody else will realize how much the clicking annoys the driver.