In the first poker scene, the very first card dealt by 'Danny Haley' lands on a short stack of chips. An instant later, after the cut to the wider overhead shot, the card is no longer on the stack of chips. (And the chip stack sizes and positions have changed).
As Fran Garland first walks into the card game, behind her, a string tied to the door which makes the door automatically close after she walks through it can be briefly seen.
Although done in medium long shot, it's obvious the man in the car is not Heston, but a stunt double.
When questioning the suspects about the suicide of Arthur Winant Captain Garvey mentions that the crooked gamblers got Winant to sign over a cashier cheque for $5000. However, there is no evidence to support this statement since the Police would not know about the cheque which was now in the gamblers' possession and Arthur's brother Sidney had removed the suicide note when he discovered the body.