It's actually the first ADB board to reach market.
On the two I have, IIRC it's the close tolerance between the keycaps and the side of the case (and to a lesser extent to each other) that can cause them to bind if hit off-center rather than anything going on with the switches - except for the contribution of the inherent looseness of Alps-style switches, of course. It's especially a problem if the case plastic has warped at the edges at all as some rougher used ones can have.
The case edges essentially come straight up to form the side boundaries of the board in a very minimalist style with not quite enough lip or reinforcement to prevent warping from sun, age, abuse, etc. Also, the design of the keycaps creates a relatively narrow space between each other as well as the board edges with lots of nearly vertical edge surface area to bear against each other that is kind of unforgiving of loose switches, warped or misaligned plastic, etc.
All such issues aside, they are really nice compact boards (an elegant if flawed design) when in good condition with an action similar to, but a bit less refined than, an AEK I.
