Factual error: Rob told Sally and Buddy that he hit "Boom Boom" in the appendix. When we see Rob punch that guy he hit him right in the upper stomach. Rob would have won the boxing match. Because "below the belt" refers to all the area of the body that lies below the line of the opponent's navel, including the groin area, legs, and crotch.
Revealing mistake: While Rob is having a boxing match and Laura is really mad at Rob. I noticed that some of the punches are actually to the hand region when Rob is in the corner and supposedly gets a boxing glove to the face. They aren't hitting each other that hard either.