Other mistake: When Ferris first arrives in the town the the church bell chimes seven times indicating it's 7 o'clock. Later the bells chime again but this time only four times indicating 4 o'clock. Surely he didn't walk around the empty town for 9 hours.
Continuity mistake: When Mr. Bookman is leaving his apartment to get away from Death, there is a note tacked to the door that is about level with his head. In the next shot, he's out in the hallway locking his door and the note has moved up to about 6 inches above his head. (00:12:35)
Plot hole: If Walter was indeed immortal from his deal with the devil then there was no reason for him to use the Escape Clause when he was sent to jail. Since he can't be killed by any means and nobody can harm him there would have been nothing to stop him from escaping the prison the moment his cell was opened.
Continuity mistake: When Cadwallader puts a seal on the Escape Clause paper, he presses so hard that he manages to lift the whole document with seal. You can see that there is absolutely nothing except for a seal mark on the paper, yet when he drops the paper to the floor some typed text appears on it. Also in the same scene, the seal pattern is square in the first shot, but when the paper drops to the floor the seal mark is round.
Factual error: Corey is in solitary confinement on an asteroid. However, asteroids are neither large enough nor stable enough to hold an atmosphere. In addition, the distance from earth stated in the episode wouldn't be much further than the moon; there are no asteroids in a stable, regular orbit around the the moon or the earth, nor around the sun anywhere that close to earth.
Other mistake: The supply crew arrives at the asteroid every 3 months, as established by the dialogue between Corry and the astronauts who bring him the female robot. However, Corry's narration reveals that he has been living with the robot for 11 months when the next supply ship arrives.