Well..... upon close inspection under magnification, I now see the problem with the last shot hold open. Both the slide stop and the notch in the slide display obvious signs of deformation where the two pieces contact each other. Instead of both parts meeting squarely, they each have a bit of angle now. I'm really surprised there is enough forward motion in the slide, at that short part of the stroke before it catches, to have caused such damage. Regardless, this one's gotta go back to CZ. If I can get any macro photos to post here, I'll show you what I found.
I don't know if this has any correlation to the last shot fail to feed issue but I guess that is a moot point now. Given the damage to the notch in the slide, I imagine they will replace the gun. Can't just replace the slide since the slide, barrel and frame all have the serial.