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.
Revealing mistake: In scene where Liz is telling captive ex-husband, Tom, that she will let him go after he helps her get Berlin, Tom gets up and you can see the chain on his leg is only held to the floor with a chain link that just screws closed.
Revealing mistake: When Elizabeth Keen removes the tape from Amalia's mouth after rescuing her, she briefly reveals the sticky side of the tape to the audience, showing another large swatch of tape attached to what should be the sticky side. This was done to prevent the actor's skin and provide easier removal.
The Decembrist (No. 12) - S2-E8
Revealing mistake: When turning the guy with C4 around his neck, the 4 person safe box window shakes briefly. If this was a bomb proof safe box, the glass would be at least 1.5"+ in thickness and would not shake simply from some walking. That box would be shrapnel to a C4 bomb inside. (00:26:30)
Marvin Gerard (No. 80) - S3-E2
Revealing mistake: In the scene where Solomon kills the Russian convoy driver in the hospital, there is a black computer mouse pointer visible over the HR/min on the medical equipment display. (00:22:23)
Revealing mistake: When Tom Keen is on the phone at the end of the episode, he is holding the phone backwards with the screen away from his ear. (00:41:20)
Revealing mistake: When Elise calls Navabi's phone, the phone is not in call mode.
The Architect (No. 107) - S4-E14
Revealing mistake: Aram Mojtabai fires a high-caliber weapon, destroying a vehicle with it. But after the weapon is fired, the projectile is still in it. Instead, the weapon's lower jaw has disappeared. (00:34:35)
Revealing mistake: Aram "hacks" an employee database via a company website - the code that's briefly visible on screen (slo-mo helps but isn't required) is just standard HTML that lays out a web page, not server commands.
