Continuity mistake: In the opening scene, the players are taking their third card of the hand before the dealer reveals their second card. (00:02:40 - 00:03:15)
Suggested correction: That's not what happened. It was a montage scene. It's not 3 different players, it's the same player and 3 different hands. Notice the card is always dealt to the same spot.
Revealing mistake: Lower-third shots of the aquarium in the background at the Delaware Raceway's sports lounge were often blurred and did not look like they matched full views of the aquarium. (00:36:05 - 00:36:34)
Other mistake: William Tillich (AKA Bill Tell) had one suitcase which could not possibly hold enough sheets (or thin blankets) to cover/wrap all the furniture in his motel room like he did. (His suitcase was not very large and also contained his clothes.) He covered an even larger area of furniture in Gordo's house. It isn't clear if he used his own sheets or just happened to find the same kind in Gordo's house.