Continuity mistake: When Aunt Mary is writing on the whiteboard at the hospital, the word "killed" changes style between shots. (00:31:40)
Continuity mistake: DI Goodman is inspecting the pillows; when he gets to the second bunk bed, you can see that handling the pillow he accidentally catches with his arm a blue piece of clothing placed on the railing, dragging it a little along the way, towards the vertical support bar. The next shot is evidently from a previous take, because that blue rag is in the initial position, away from the bar. (00:39:10)
Continuity mistake: When Goodman sprints away from the banquet, the cue cards in Dwayne's hand move from both hands to a lowered left hand in the faraway shot. (00:38:40)
Continuity mistake: When Goodman jumps up yelling "yee-haaw!" messing the wedding table, Commissioner Patterson grabs a towel with his left, but at the cut he is using the right hand to clean his left. Likewise, Florence has in the second shot a hand on her chest, but she didn't have that pose already in the previous, it was just her initial reaction. (00:38:00)
Continuity mistake: Humphrey gets next to Leo's bed saying "Hey sexy." He has a hand in his pants and the other on the phone, but they swap place at the first cut. When he gets up and protests that he loved Sian, the phone disappears. (00:39:10)
Continuity mistake: After hearing about the theory that perhaps Sian and her knew each other from back home, Perrie Campbell walks away. Goodman grabs the manuscript from the table, but his arm does not move in the reverse shots. He then puts it back, but when it is his turn to stand up, it is nowhere to be seen - yet it didn't look like he could have put it back much far away. (00:16:55)
Continuity mistake: When Perrie Campbell says "Now I can see it", about the world out there, the bang on her right side is windblown. The wind is instantly absent in the next shot, just as in the rest of the shots from that angle. (00:16:35)
Continuity mistake: Dwayne has his fingers on a different spot of the evidence bag with the ecstasy when the camera angle changes. (00:15:05)
Continuity mistake: Humphrey brings attention to the toiletries when asked why does he not quite believe it was suicide; in close-up the bag is in shadow, but in the wider angle there was direct sunlight on the top of the bottles. (00:05:45)
Continuity mistake: When Perrie Campbell tells her much younger friend that she can still drink her under the table, a bottle of beer suddenly appears in her hand. During the rest of the exchange the beer bottle in Sian's hand faces different directions each shot. (00:01:05)
Continuity mistake: During the first scene, Sian Evans' hand is around the bottle of Etensel or flat on the table, depending on the angle. (00:00:45)
Continuity mistake: At the beginning of the episode, Perrie shows the moth tattoo to Sian. In the close-up of the lepidoptera, Sian's elbow is barely off the corner of the table, but she's leaning with just the hand in the following shots. (00:00:40)
Continuity mistake: Addison Patrick pulls out of his pocket a bag with the coins. A string dangles off his palm, but when he hands it to Florence, the strap has been pulled up. (00:30:20)
Continuity mistake: Goodman calls it a day and mentions the stag party. Dwayne lays out on the desk three pair of handcuffs; the leftmost (the first he put down) is apart from the others, but when the lube comes into play, all three are clustered together. (00:22:35)
Continuity mistake: Florence puts on the table the knife sheath; it is laid out with the ends of the belt apart, but when Newton Farrell answers, they are joined together without anyone having touched it further. (00:20:30)
Continuity mistake: Humphrey found the cigar butt inside Newton's ship. He goes with his ever-smiling sidekick to interrogate him, finding him in asleep with a flask of booze between his hands. Cut, and Roger Griffiths' hands are on top of the flask instead than the bottom. (00:20:10)
Continuity mistake: Florence finds the divorce papers and calls Humphrey's attentions on them saying "Sir..." There is a paper sheet leaning by a corner on the laptop's right side. When the tabletop is again in frame (when Humphrey puts the coin back in the safe) the papers are arranged differently. (00:18:30)
Continuity mistake: The police are inside Tosh's boat, and Naomi Walker pokes downstairs to tell them that all his stuff is there and to help themselves. She has both hands on the manhole, which becomes just the right hand at the first cut. (00:17:25)
Continuity mistake: Humphrey grabs the ashtray in the boat; the cigar butts are placed differently on it between shots. (00:17:25)
Continuity mistake: Sam Walker is holding back his dad Tosh, pulling him apart from the rival Newton Farrell. When Tosh snarls "Get away from my boat", his son has his left hand on his shoulder, but it's behind his back in the intermediate reverse shot. (00:01:25)
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.
raywest ★