Other mistake: Jack follows J. Edison Nash to a wine warehouse and watches as Nash punches numbers on a keypad in order to gain entrance to a private room. Nash punches the 6 and a beep is heard. He then punches the 8 and another beep is heard. During a close-up of Jack, four more beeps are heard, for a total of six. Jack says the number out loud - 862, which is only three digits.
Continuity mistake: In an interior shot of the detectives' vehicle, the car is a late 80s Chrysler (LeBaron or K-Car), obvious from the 'pentastar' logo on the steering wheel and the distinctive gauge layout. When the detectives walk away from the car, it is the homicide standard issue Chevrolet Cavalier.
Character mistake: Trivette hands the man in yellow a bullet recovered from the plane Walker and Alex were traveling on, which was shot down by an assassin flying a P-51 Mustang. This man, and later Trivette, mistakenly refer to the round as a "50mm," when in reality, Mustangs were equipped with M2 Browning .50 Caliber (12.7 mm) machine guns. (00:30:25)
Show & Tell - S6-E10
Continuity mistake: During a conversation with Diane, Jill says that her son is with his dad. In the conversation she calls the dad "Ken." In future episodes Jill's husband is called "Don." (00:03:55)
Continuity mistake: In an earlier season Caine takes a young Peter to a place in the temple and explains that his mother is buried there. However in the series finale he shows adult Peter a picture that someone took months ago and Caine tells Peter that the woman is his mother and he's going to find her.
Plot hole: "Showdown": Darien's lost hat and jacket reappear without explanation after Kane finds him wandering in the desert. Also unexplained is how Kane conveniently happens to be leading an extra, unnecessary horse - unnecessary, at least, until he stumbles across the stranded Darien. (00:15:00)