Continuity mistake: When Early Smith runs out of the supermarket and shoots one of the three thugs, he lowers his gun after killing the thug. In the next scene, he is holding the gun back in a raised position.
Continuity mistake: When Harry, dressed as an overseas pilot, enters the aeroplane during the hijack scene, one of the hijackers draws his gun right in front of Harry when he says "Good afternoon". In the next scene, the gun is further away from Harry than it was in the previous shot.
Continuity mistake: When Lt. Briggs is being interviewed after the swimming pool massacre, we see a close up of Briggs and there is a man with a moustache next to him. But when we cut to the next shot where Briggs is on television at Carol McCoy's house, the man with a moustache has suddenly disappeared.
Chosen answer: The error didn't necessarily start with the makers of the credits. It could have crept into the process at any point. Whoever typed up the names to give them to the technicians who made the credits could have misspelled the name.