You can find some pretty interesting improperly redacted documents all over PACER. Usually it's defense attorneys who don't realize that blacking out text in Adobe doesn't remove it rather than the government though.
There's one about a Colombian paramilitary leader/drug trafficker turned informant which improperly redacted all the people he informed on: https://storage.courtlistener.com/recap/gov.uscourts.dcd.184.... This is from like a decade ago but goes to show how this kind of thing can literally put people's lives at risk.
https://www.goodreads.com/book/show/41181600-the-mastermind