Continuity mistake: DI Humphrey Goodman writes the name of the victim on the whiteboard, in a close-up. He then starts enumerating the suspects, but the name changed penmanship - look at the odd shape of the E linked to the previous letter, or the suddenly shallow M. (00:13:50)
Continuity mistake: Rosey Fabrice visits the police station the morning after the murder. Dwayne puts his moves on her and places his hand on the back of her chair, but in the close-ups his arm and hand are simply not there. (00:12:10)
Continuity mistake: Humphrey and Florence are checking out of the crime scene the morning after. When Florence says "Also, if she's telling the truth" the pen did a 180° turn in her hand; it had the ballpoint up, now it has the cap. (00:10:45)
Continuity mistake: When Humphrey turns towards Florence to mutter instructions about checking the case with the UK police, Joséphine Jobert's hand is positioned on the top side of the notepad, and in a different position at the cut. (00:09:50)
Continuity mistake: Sadie Mernier tells the police about the victim's stalker. In close-ups, her large hoop earring is caught between her hand and her face. Camera further back, and the earring is on the outside. (00:09:35)
Continuity mistake: In the intro, Zoe appears all of a sudden by the stage entrance; the other two models were on the runway with nobody there before the cut. (00:00:15)
Revealing mistake: When Humphrey checks out of the mail from the dating website at the end of the episode, behind the window of the mail client, there's a fingerprint file with the name "Adam Frost" and a 2014 sampling date; it's a file recycled from two seasons before, 3-4. (00:49:55)
Continuity mistake: During the opening party, extras are recycled - in particular, a man with a white fedora appears multiple times, sometimes with shades, other times not. (00:02:00)
Continuity mistake: Humphrey writes the various names on his whiteboard. In the close-ups that immediately follow (and in those later in the episode, but days have passed meanwhile so it's more understandable) the letters have partially faded. (00:14:15)
Continuity mistake: Humphrey tells Florence to stop the car and points at Andy Hammond. As we see him through the dirty window of the Defender, a couple (woman in pink tee, man in pattern blue and white shirt) passes by him. When Humphrey opens the car door, they are in the background, far away. Next shot when he begins his short lived tailing, and those guys are again passing the politician by. (00:35:35)
Continuity mistake: Dwayne hands DI Humphrey Goodman the telephone with the pictures of the drill holes; in close-up, Goodman's fingertips are barely against the sides, while in the other shots the fingers wrap more closely around the device. (00:23:55)
Continuity mistake: When Florence answers Humphrey's question about the french word for "affair", she is holding her pen in hand with the thumb at the bottom. Next shot, with the enraged president standing up, and she's placid in a different position, her hand turned to support her chin. (00:22:20)
Continuity mistake: When Humphrey explains the findings of the post-mortem, he speaks waving his right arm around - in front views, because it's the left when the camera is behind him. (00:14:40)
Continuity mistake: During the rendition of the Commissioner's movements with the glasses, he says in a faraway shot that the governor "was standing with Andy Hammond." Before it cuts away from this shot, you can see JP handing the appropriate photo to Goodman seconds before it actually happens. (00:09:50)
Continuity mistake: Commissioner Selwyn Patterson holds the glass and bottle at a different height in the wider shots (fingers are at the champagne level in the glass) and in close-ups (glass about an inch fuller). (00:03:50)
Character mistake: Humphrey tells the riddle of the two barbers wrong; you have to set it up saying that the 'good' barber has a great haircut, not that he's great at cutting hair, or you negate its point (which is that the 'bad' barber with the bad haircut is the one who did the haircut to the good-looking barber, and vice-versa).
Continuity mistake: Humphrey, triumphant for the discover made through his gossip with the roomie of the suspect, slams the yachting magazine on the desk with a swift motion of his right arm, which is the left arm in the next shot. (00:37:25)
Continuity mistake: Early morning at the station. Florence just arrived, and Humphrey is telling her about his suspicions on Nicky Hoskins. She replies that she needed the job; between shots there's an obvious difference in the positions she listens in. She is palm to back at first, then both palms upturned. (00:36:50)
Factual error: The website of the toy manufacturer has as address for its store a location in Harrogate, but the ZIP code has an incorrect format, with the 4th character being an O and not a zero, and HG4 being the neighbouring Ripon. (00:28:30)
Other mistake: It's played as a gag, but still it's quite inconceivable that in "fifteen minutes" it would get pitch dark so that Dwayne can avoid his duties sanding the ship! How much time could he have bought even if he had more excuses up his sleeve? Goodman really can't tell the difference between 15 minutes and a couple of hours? The scene started when it was nowhere near dawn. (00:21:10)
Answer: There's probably no particular reason. Sets and props on long-running TV shows often change as needed and for various reasons throughout a series run.
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