I've never had this issue with a CZ (Series 70 Colt, yes, more later).
It looks like the slide is not hitting the rear of the case as the slide moves forward. It hits the side of the case and drags it forward/upwards out of the magazine but striking the case in that manner it cannot chamber the round, it just hangs up sort of sideways with the bullet up and the slide against the side of the case.
Anyway, a couple things to check. First a question: When this happens is it somewhere in the first few rounds, the middle of the rounds in the magazine or the rounds near the bottom of the magazine.
I ask, because, as someone who sometimes unloads a full magazine or two to clean the insides I've seen/felt some magazines get real "draggy" as you thumb the rounds out to empty it. The feed upwards nice and strong at first, then you begin to wonder if the rounds are going to pop on up to the feed lips and then after you get past those 3 to 5 rounds that seem to hang/drag the rest of the rounds move upward nice and strong again.
Questions now:
1) when was the last time you took the magazines apart and cleaned the insides out?
2) have you ever stripped the oils/dirt off the magazine surfaces (inside and outside) and used car wax (a couple good coats inside and outside - just like you'd wax your car/truck) to both protect and slick up the interior surfaces?
I just recently started waxing (a few) of my CZ magazines and I can't promise it will fix your problem. I did mine for rust/corrosion protection issues (I sweat a lot and my spare magazines come out of the pouch with sweat drops beaded up all over them). Other folks here have reported that waxing the inside and outside of their magazines helps keep them cleaner and functioning smoother.
Good luck with it. It can absolutely be fixed as many people never report this issue, so there is a cause and a fix.
