Revealing mistake: In the arcade the killer talks to his helper while playing a pinball machine. He plays very agitated and strongly. But if you look closer at the below end of the playfield you see that there is no ball and the flippers aren't moving. (00:23:50 - 00:24:48)
Quincy M.E. (1976)
1 revealing mistake in Vigil of Fear
Starring: Jack Klugman, John S. Ragin, Joseph Roman, Robert Ito
Go Fight City Hall -- To the Death! - S1-E1
Factual error: When Quincy, the well-experienced doctor, uses the defibrillator to bring a just deceased man back to life, he never put some gel on the paddles in the first place. (00:15:25)