I purchased a 1992 Pre-B CZ75 some time ago.  When I got it, I found that it was suffering from failures to extract.  The casings would get about halfway out of the chamber, then get stuck, while the slide would continue rearward and attempt to pick up the next round in the magazine.

I replaced the extractor, as well as the extractor spring with (I think it was) a Wolff extra power spring.  I noted that the extractor retaining pin fit in the slide was quite loose compared to what I was used to, to the point that it could be pushed out with little more than hand pressure on a punch.  Regardless, the failures to extract seemed to stop happening.  

Some time later, during another shooting session, the extractor retaining pin actually began to back out while firing.  It was suggested to me that I put Loctite on the pin and reinstall it, so I did that, using blue Loctite.  I believe the pistol worked fine for a while after that, but I do not recall for sure.  

Then, during yet another shooting session, I began to suffer from failures to extract again.  The casing gets about halfway out of the chamber, then gets stuck, while the slide continues rearward and attempts to pick up the next round in the magazine.  Thinking that perhaps there was buildup under the extractor causing the problem, I removed the extractor and cleaned it, the extractor cutout in the slide, and the extractor retaining pin.  I then reassembled it, staking and putting a slight bend in the extractor retaining pin to help it stay in place without the use of Loctite.

At yet another shooting session, I found that the problem had not been resolved.  I tried cleaning the chamber of any hard buildup by scraping it with a brass tool, but that did not seem to fix the problem.  Additionally, I experienced a few failures to eject, where the casing gets extracted, but then stuck in the ejection port, oriented in the same direction as the gun.

I field stripped the gun and placed a cartridge against the breech face, under the extractor, and shook it.  The cartridge stayed in place, so the extractor tension still seems good.  Offhand, I didn't notice any damage to the extractor, but given that I don't recall noticing any damage to the original extractor that I replaced to solve my earlier failure to extract problem, I'm not sure I am competent at identifying extractor damage.  Additionally, this problem does not seem to be magazine related, as I experienced it with multiple magazines. The malfunctions happen maybe once out of every twenty to thirty rounds fired.

The only thing that really comes to mind that might be causing this issue is damage to the (replacement) extractor due to the slide being dropped on a round that was manually loaded directly into the chamber, as I recall a friend of mine might have done when I let him try the gun.  Unfortunately, I don't shoot this gun enough to remember the specific history with great detail and accuracy.  

Before I go and buy another extractor, does anyone have any ideas as to what else I might check out?  Is dropping the slide on an already chambered round particularly damaging to the CZ75 extractor?

What ammo are you using. Winchester is known for causing problem in CZ's

The other thought is to polish the chamber with Flitz on a rod and cloth attached to a drill.

I don't know if it will hurt the extractor but it sure cuts a chunk out of the brass rim.  I did it once (done it for years on my 1911's) on my P07 but won't do it again.  A chunk of brass that size could fall down inside and hang something up.

Lock the slide back, insert a magazines, point in a safe direction and either hit the slide release or pull back on the slide and then release it.  Then put it on safe, drop the magazine and add another round to the magazine and re-insert the mag. into the pistol = good to go.

Have you (since letting the slide go forward with a round in the chamber chops a chunk of brass out of the rim) got a piece of brass hung up under the extractor?

Have you checked the chamber to see if there is any damage or roughness? I have a Tanfoglio TZ75 that I bought years ago. The previous owner had tried to "clean" the chamber with a steel brush. I had many extraction problems until I finally replaced the barrel with a CZ factory one. I also have a FN HiPower from around 1950 that had extraction issues. It turned out to have some pretty extensive pitting in around a third of the chamber, particularly on the upper side next to the throat. I had to replace the barrel on that one as well.

Thanks for the responses.

I tried it with Herter's (OEM by Sellier and Bellot) and Blazer.  Both brass, both 115 grain, I believe.

When I cleaned under the extractor (when I removed it,) I did not notice any unusual debris.  Just some rather thick black buildup that I scraped away with a punch.

When I inspected it at the range, I noticed no damage to the chamber.  I am not able to check again at present.

Having done more research, I am increasingly suspecting that this problem is the result of damage to the extractor as a result of the incident mentioned in the original post.

New extractor.  The claw end is more than likely broken

I would try polishing the chamber first though.