The first type of failure is a bolt-over-base malfunction, which I've most often seen when bolt velocity was too high. However, without seeing it myself, it could also be caused by a short stroke, which would indicate that bolt velocity is too low, lol.
The second failure you're describing makes it sound like the issue might be short stroking, perhaps due to gas leaking from in between the barrel's gas port and cylinder instead of driving the piston.
My best guess is that the issue is related to a worn gas cylinder. My amateur, non gunsmith recommendation is to get CZ to take it back for warranty work. Failing that, the first thing I'd try is replacing the gas cylinder and continue to diagnose from there if necessary.