Revealing mistake: During the attack on the Range Rover in Shanghai, China, none of the passers-by react to the gunfire in any way. An automatic weapon's unloaded into the windshield, then a window smashed with a pistol fired through it, but people on both sides of the street don't even look up, they just keep on shopping. The attack was clearly composited into generic footage of a city street. (00:00:50)
General Ludd - S1-E8
Revealing mistake: After Reddington kills Elizabeth's father and kisses him goodbye the "corpse" takes a deep breath.
Answer: The man Red killed, Sam Scott, was Lizzie's adoptive father, not her biological one. However, at that time Lizzie (and thus the audience), was led to believe her real father abandoned her and her mother, so expect more secrets to be revealed how her real father actually died (or if he's even actually dead).
Bishop73