From my dealings with CZ, they've bent over backwards to be helpful. I've spoken with Mike Eagleshield, the head gunsmith, several times, and he explained to me the exact procedure for detail stripping a 75B, including what to watch out for in reassembly because of the pins. He also courteously answered all of my questions regarding the 85 Combat and CZs in general. These are good people who spend a great deal of time talking to weapons enthusiasts like us.
Still, I can understand jrf's concern over a handgun that doesn't work 100%. Been there. It's frustrating. If the handgun still fails to extract after installation of the new extractor, send it back to CZ for repair. I'd be extremely suprised if it wasn't returned to you in perfect working condition. If you give CZ a reasonable chance to make it right, I'm sure that they will.
As to the terms "design flaw," even if CZ brought it up, let's not take it out of context. An extractor that gets dirty after shooting isn't even a mild issue. As to this particular CZ Compact's failing to extract, name any of the best handguns in the world, and I'm sure that I could find someone somewhere that got one that didn't work perfectly. In fact, any handgun in the world could be changed in some way to make it a little "better" ....... gunsmiths are our friends.
Last, I'd like to thank jrf for sharing the information with us. Let's not shoot the messenger. Everyone here, including jrf, has an extremely high opinion of CZ firearms. We can take and evaluate the information as provided. My conclusion is that it's an anomaly that that CZ will fix it.
Good luck!