Other mistake: About half way through the movie, Adrian gives Rocky a dog (Butkus). The second time Rocky goes to the meatpacking plant, the dog is with him when he walks in, but he walks out alone and the dog is not seen again in this movie.
Suggested correction: How is this a mistake? Rocky could easily have left with the dog on another occasion. It's like saying, sometimes Rocky is shown in a location but it's never shown how he got there. That isn't a mistake, it's just what happens in films. Also, the dog not being seen again is irrelevant.
Other mistake: After Paulie gets mad in his place using the bat, he breaks the lamp and the room goes dark, but there's a second lamp which should be illuminating the room.