Other mistake: Even though this is a fictional event of how Billy Batts was murdered, he was a made man in the Gambino Crime Family. So, it doesn't make sense for him to have a party of him coming home from prison at a rival family's establishment, meaning Henry Hill's club, which was a Lucchese Crime family hangout. He would have had the celebration on his own turf, around his own family.
Suggested correction: While there is no way to prove how factual it actually is, this is almost exactly the way the real-life Henry Hill told the story in the mafia memoir, Wiseguy. The only differences being that Batts was not killed that night, but a couple of weeks later, and Henry did not own the club, Jimmy did.
Well, that isn't at all the disagreement here. My only concern was, why was a Gambino made man having a party at a rival family's establishment and not on their own turf? That's the blooper here.
Character mistake: In jail when they're all sitting down to eat, Paulie says "c'mon boys let's eat, Freddie, Vinnie let's go" The problem is the other guy's name is Johnny Dio, not Freddie.
Other mistake: When Tommy kills Stacks, after he leaves the apartment, they re-enact the murder from a different camera angle in slow motion, where we see Tommy's face. Right before Tommy starts shooting, we can see blood stains on the wall already.
Continuity mistake: When Karen is pointing a gun in Henry's face, the close up is different from the one she has in her hands. (01:13:00)
Factual error: Unless Henry was intoxicated or heavily medicated during his sleep, it would have been impossible for Karen to have climbed on top of him in bed, point a gun at his head, without him ever feeling her body on top of his.
Continuity mistake: Henry picks up Karen from a phone booth after her neighbor tries to attack her. The left side of her shirt is dirty. When Henry drops her at home and beats up the neighbor, Karen's shirt is completely clean. (00:39:36 - 00:41:10)
Continuity mistake: After Henry gives Paulie a share of the money he took from the air port, Paulie tells him to say that he got the rest of the money playing Craps in Vegas. Paulie's left hand is around Henry's back with his hand flat out on his shoulder. When it cuts to a close up as Paulie is playfully slapping his cheek with his other hand, his left hand is now suddenly balled up in a different position on Henry's shoulder. (00:35:30)
Revealing mistake: Young Henry's eyes are distractingly bad with obvious contacts that look really fake.