Not unheard of. Agreed.
Design flaw? Who knows? For as I said above, I've put thousands and thousands of rounds through my CZs without the first extraction problem.
Should the design be such that cleaning shouldn't be required?
I put 2,000 rounds through my CZ-85 Combat once, just for the hell of it, without cleaning. No extraction problems.
I suspect there may be problems with specific extractors, maybe made NOT exactly to spec.
Is that a design flaw? Probably not. Is that a quality control problem? Perhaps. But its not a problem that is unknown to other guns, etc.
If it'll make you feel better, call it a "design flaw."
But I think if it were a design flaw it would be far more common.
I'm one of the moderators on the CZ Forum. We have several thousand registered users, and many, many more participants.
The extraction issue has come up a number of times (TENS, not HUNDREDS, of inquiries), as have problems with premature lockback (again, TENS, not HUNDREDS of times).
The guns have remarkably few problems, otherwise. This is especially amazing since many of the shooters on the CZ Forum are relatively new to semi-auto pistols, which generates a lot of VERY BASIC questions and problems.
I've had SIGs, Glocks, Berettas, S&Ws, etc., I prefer my CZs. They just fit me better. I can understand why others might feel differently.