Your problem sounds familiar, and is most likely due to counterfeit mags. There are a plethora of them out there, at $20-$40 each, that are not worth 10 cents. They are made to look like original CZ, and many of them have markings to fool us, i.e. 'MFG CZ'.
The real CZ surplus mags have the stamped bayonets along the bottom, but many of them are half worn out nowadays. Brand new, real CZ mags are available through CZ-USA, and are same as the milsurps, but without the bayonet stamp. They are available at CZ-USA and Greg Cote LLC. Anything else is junk.
The counterfeits tend to work OK for a few mag loads, then start to bend and distort, which is where the problems begin. There is a 99 percent chance real CZ mags will take care of the OP's feeding problem.