Perhaps an assembly error in manufacturing.
Some of these, probably not Leviton, are sold as individual components to be assembled when installed.

Here is a link that might be useful: Despard

I'm thinking something was assembled incorrectly at the factory but I thought I'd check. Leviton's catalog doesn't specifically say and I don't see multiple versions of that style of switch (other than, obviously, color or amperage).

Definitely not Despard.

Or perhaps installed wrong. I don't see how they could be assembled wrong.
Tell us how you have it wired and exactly how it works. Does one of the switches need to be on for the other one to work?

I don't see how it could be installed incorrectly. It's a simple SP switch/SP switch combination device. One switch controls one set of lights, the other another set. At first I thought it might be a SP/3-way combo but both toggles are marked "on" and "off". The only thing odd is that off is to the left on one of the switches and to the right on the other.

This must be one of those fair and balanced switches manufactured by Fox NewsCorp.

I heard they were being recalled because of reports of serious injury when either switch is turned to the left.