Revealing mistake: Any time any character is driving a Suburban, or any other vehicle with a column mounted shift lever, the shifter is in park while they appear to be driving.
Night of Desirable Objects - S2-E2
Revealing mistake: When the typewriter is being used at the end, the keys being pressed don't correspond to the words appearing on the paper. Obvious from the start - the first letter pressed is on the middle row of the keyboard, but the first word typed is "unacceptable".
Revealing mistake: Near the end of the episode, when Dr. Ogden and Murdoch look closely at Lukas' dead body (right before the candle scene), the "corpse" takes a deep breath.
Revealing mistake: In the morgue when Mike is just about to cover the first dead body, if you look closely you will see the body's eye move. (00:04:10)