That's new! I would have to say either the mag release spring is weak, or the cutout in the mag body is shallow/malformed.
Did you buy this new or used, as a new one SHOULD have come with two mags. Contact CZ-USA, and ask to speak to Mike Eagleshield, the CZ gunsmith, about this. Ifit's new, ask for a replacement mag, (and find out what you dealer did with the other mag, which sells for over $35 each!)
Hope that helps!