That's a very interesting observation. The implication is that it is probably futile to keep ordering and returning recently manufactured N9s in hopes of finding one without the loose button problem.

Since it is clear that the loose buttons are considered a "feature, not a bug". Is there anything that can be done to stiffen them up similar to the N9s manufactured during the earlier runs? As someone in the US, I don't care about voiding my warranty and am willing to open the phone up if there is an easy fix...