When Sam is first told by one of the brothers that "Mundy" had arrived, Al then explains to him that it would be Clyde Mundy, the Chief of Police. Shortly after that, Sam talks to Clyde by phone, as Clyde is in the diner. Sam calls him Chief Mundy. However, after his conversation with Sam, Clyde hangs up the phone & requests of one of the waitresses that she get him a piece of pecan pie, to which she responds, "Sure, Sheriff." In the next scene, as Clyde sits down to eat his pie & coffee, the husband of one of the bank employees comes in & immediately addresses him as "Chief." Also, it can be seen that Clyde's badge is the traditional "shield" of a local police officer & not the "star" of a county Sheriff's Department.
When Sam is pacing around Gus Vernon's office talking to Al, you can see a shadow of Al cast on the door frame. Al being a hologram should not cast a shadow.
When Sam is talking to his dad, you can tell in the shots of "Sam" from behind he is played by a different actor - the hair is wrong.