The Murder's in the Mail - S1-E6
Factual error: Dead blonde guy is sitting upright in the chair, as Dave/Maddie close in, and Maddie realises he isn't moving. David goes to him and smacks him across the shoulder, to "wake him up" and blonde dead guy, right on cue, instantly slumps over a table at his right side, when the direction that David hit his shoulder, should have sent the dead guy slumping more forward, then at the front edge of the table. Obviously staged for the actor's comfort.
Song of the Younger World - S2-E20
Factual error: The 19th Century reformatory has modern electric light bulbs hanging from the corridor ceilings. (00:21:10)