OK, so it seems these were built in two different iterations. One, a straight up copy of the CZ-75 Original are pretty difficult to come by here in the states, and the other which is what you have, a "copy of the copy" built on the Tanfoglio pattern. Interestingly, the legend goes that ITM simply bought unfinished parts from Tanfoglio and finished them out in Solothurn. If true, (and I have no reason to doubt it) then your problem should be easily addressed. We've seen a number of Tanfoglio pistols with broken ejectors here so in my mind that tends to reinforce the idea of Italian parts. At the heart of it, your AT84S is a Tanfoglio, just with Swiss levels of fit and finish, especially externally.
The CZ copies were all Swiss made and evolved into what is currently being imported by Sphinx, the successor company to ITM.
Addressing your issues: Obviously needs a new sear housing cage/extractor. I'd second Grendel's suggestion for all new springs all the way around-older Tanfoglio springs seem to be a weak point. Pull the extractor, check for claw damage and debris in the channel, new spring. Check the chamber for scoring or burrs. Clean the snot out of the whole gun-who knows how long it's been sitting with a broken extractor with the oil gumming up and collecting dust bunnies.
Sounds like a pain to do but those AT's are gorgeous guns, and well worth the effort.
Oh, and I'd certainly have a word with your seller from Gunbroker. We don't know if they knew it was broken or not, but I'd absolutely let them know about the condition of the gun as received. I think I found your auction and that seller sells a lot of guns so probably had no idea, but you should let him know about it.
