Continuity mistake: When we first see John, he is in the police shooting range. He has on protective head phones which he takes off and sets on the table in front of him as the other cop comes in. He and this cop talk about Jack, and when they finish, they shake hands. The mid range shot of them shaking hands shows the head phones still on the table. It then cuts to a far shot and now the head phones are gone while the two finish the hand shake. Careful which table you are looking at, as the angle makes it confusing. The head phones were on the table with the red thing on its left side.
Audio problem: In the scene in the banquet hall, where the bad-guy is eating a carrot, he throws it on the floor. Subsequently, while chewing on the little bits he has left in his mouth, there comes a sound which is not a chewing-small-pieces-of-carrot sound, but a biting-a-piece-off-a-carrot sound. That sound was way too loud to have been produced by some little piece he had left in his mouth.
xx:xx:xxJacob La Cour
Plot hole: When Jack and John are on their knees in the hotel, with their hands zip-tied behind, Jack manages to use a hidden knife to cut his bindings and starts kicking bad guy butt. Jack immediately joins the fray but a careful review shows that at no point did John use his knife to free Jack.