Factual error: Lieutenant Colonel Mann explains to the NCIS team that a "99 Toyota" is the only unaccounted for vehicle from the golf course bombing. The vehicle is a Toyota but is obviously a mid-80's Corolla, with the last production year being 1987, making it over a decade older than Mann claims. Additionally, she would not have know the year of the vehicle prior to the team running the plate, nor would she have pointlessly assumed its year. (00:32:06)
Continuity mistake: When Gibbs rejects the agent's file, Cynthia reaches for the ringing telephone with her right hand and Gibbs stops her with his left hand, but in the closeup Gibbs has his right hand on Cynthia's left hand. The closeup is a flipped shot, note their watches. (00:03:05)
Lt. Jane Doe - S2-E4
Plot hole: It really doesn't make sense that they found the real killer from Jane Doe #1 assuming he also killed Jane Doe #2. They only found him because they assumed he was in prison for the last 10 years. One could explain that he must have gone to prison shortly after the first murder because he said he'd be back but wasn't, but that he was actually recently released is just pure coincidence. And without finding him they would never have suspected Officer Cluxton.
Masquerade - S7-E14
Continuity mistake: When Gibbs has got the numbered yellow cones at the crime scene, they alternate from on his bandage to his hands between shots. (00:03:40)
Masquerade - S7-E14
Continuity mistake: When McGee is at the online wedding, a man with a green shirt and blue folder can be seen walking down the steps behind him. The same man can be seen preforming the same action a few seconds later. (00:03:00)
Continuity mistake: The amount of foam atop Ton'y beer when talking to his dad is constantly changing. (00:18:20)
Nine Lives - S6-E5
Continuity mistake: When Fornell walks past the reporters at the court house he passes The Wall. Camera cuts and he has jumped back and isn't near The Wall. (00:36:30)
Character mistake: We see McGee searching on his computer and the phrase "violaters will be prosecuted" is seen below the search bar. The word violators is misspelled. (00:14:50)
Keep Going - S14-E13
Other mistake: While panning the front of Gibbs' home, the roof of one vehicle and the windshield/passenger mirror of a second can be seen behind the gate/fence in Gibbs' driveway behind his truck. He lives alone and does not share a driveway with other homes. In reality, Gibbs' home is located at 2647 S. Magnolia Ave in LA, and the vehicles likely belong to the real residents/homeowner. (00:39:20)
Factual error: After Gerald gets back to NCIS HQ, he notes that he wasn't able to drive Ducky's Morgan; a stick. Abby brags about knowing how to drive a stick since she was ten. When asked what she drove that had stick, she answered, "Red '47 Ford half-ton with four on the floor and Bubba riding shotgun." When asked who Bubba was, she answered that he was the best coon dog in Jefferson Parish. If in fact Abby grew up in the city of New Orleans, as stated by McGee in the episode before, the dog would not have been the best coon dog in Jefferson Parish but Orleans Parish. No part of New Orleans is inside the Parish of Jefferson. If it was truly the best coon dog in Jefferson Parish then Abby would have lived in Metarie or Kenner, Louisiana, both of which are inside the parish limits of Jefferson Parish.
Kill Chain - S11-E12
Character mistake: Ellie Bishop introduces herself to Delilah as Emily Bishop in the elevator scene. Her name's Eleanor in the series, but the actress' real name is Emily. She used her real first name in the scene.
Suggested correction: Ellie correctly says, "I'm Ellie Bishop," when she introduces herself to Delilah. I slowed the speed down to 0.5x to confirm.
Visible crew/equipment: At the very start as the woman walks round the car a boom mic dips into view. (00:00:05)
Suggested correction: Please rewatch this scene. It's not a boom mic, it's the vehicle's antenna topper.