Continuity mistake: Laura Hagen is back in the cabin to retrieve the sample bag she forgot. The bag was under a map on the table, which she moves by a whole lot...or just a tiny bit, when the table is shown from another angle. (00:02:25)
Continuity mistake: Humphrey and Florence go back on the boat after the preliminary interview. Florence is on the phone with the Coast guard when she gets on the boat; the phone is on her left hand, and the right hand is occupied by the notepad. When she tells Humphrey the coast guard's report, they have traded places. (00:09:20)
Continuity mistake: Dwayne mentions enlisting the help of the Saint Marie diving school. At the following cut, his shirt is more open, revealing more of his trademark tank, and he is holding the notepad where it would have been visible in the close-up. (00:09:55)
Continuity mistake: Dwayne points his finger at JP telling him his former superior said "a policeman can't have any weaknesses." Reverse shot, and Dwayne's hand is nowhere in sight, but it is a moment later. (00:16:30)
Continuity mistake: On the derelict boat, Humphrey invites Dwayne to do some sanding together, but Dwayne has a counterproposal. Humphrey listens to it with his hand on his hip, away, on the hip again. (00:21:15)
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)
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: 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: 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)
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: 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: 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: 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: 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: 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: 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)
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: 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: 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: 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)
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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