The Thing That Happened
It didn’t take long to drill down to the issue at hand: The original Kailh Box switch specification had the X-axis thickness of the cross stems at 1.3mm with a manufacturing tolerance of +/-0.02mm. However, that specification had changed. Back when Kaihua was working to get its (then new) Box switches onto shipping products, Dareu was its first major customer. Dareu wanted a little more girth from the Box switch stems for its own keycaps and asked Kaihua to alter them. The switch maker obliged, adding tiny nibs to the tips of the cross stems to increase the thickness from 1.3mm +/- 0.02mm to 1.32mm +/- 0.02mm. Since then, all Kailh Box switches have been manufactured to the new thicker specification.
Therefore, in the original specification, Kailh Box switches would be within spec if they measured between 1.28-1.32mm. In the new specification, that changed to 1.3-1.34mm. Once this information came to light, the consensus was that the cross stems on some Box switches were a wee bit too thick, and that was enough to crack caps. If that was the case, then Kaihua screwed up. The company certainly seemed to admit that it made an error, and they immediately agreed to change the Box switch spec back to the original 1.3mm +/-0.02mm, by simply removing the nibs.
This is the new specification:
Of course, that’s little consolation to the many people (and vendors) who were stuck with what appeared to be keycap-cracking Box switches. But is it all much ado about nothing?