Had the exact same problem with a NIB CZ83 .380, reproduced the problem with several types of ammo, cleaned and recleaned the gun and the mags to no avail, etc. Happened with both magazines that shipped with the unit.
New mags (under warranty) from CZ greatly reduced the problem, which now only happens once every now and then. The problem will probably be totally gone once I get around to a new recoil spring.
Was a real bummer as I was sold on the gun's reliability as reported at this forum. I'm still a believer, but suspect a run of 83's went out with bad magazines.
Does your 83 fling brass into outer space?
Tristan