Audio problem: In an empty golf course, at such a close distance as shown, there's no way Miss Plenderlieth would not hear Hastings calling Poirot, who "lost another ball." (00:41:20)
Four and Twenty Blackbirds - S1-E4
Continuity mistake: Hastings carries the picture of the two brothers from Dulce to Poirot holding it by the bottom, top, side, depending on the angle. (00:13:45)
Continuity mistake: The story as presented would be impossible. In the story, Poirot tells his audience that the victim was dead at a time which is earlier than the time that he later tells his audience the victim was killed. (00:37:00 - 00:44:00)
Other mistake: The closing credits on the DVD are for another episode, "The Kidnapped Prime Minister." (00:47:15)
Factual error: The prologue shows the dubbing of a newsreel by a narrator. Ten years later it's 1936. But in 1926 Hollywood was still experimenting with sound film, and a UK news reel would've been silent. (It was 1929 before any sound films were made in Europe).
Plot hole: Much like the 1978 movie adaptation, in this version there is an absurdly short time elapsing between Linnet leaving the bridge table and the incident and murder; it's barely two minutes when she'd have to go to her cabin, do everything a proper lady of the time would do to prepare to go to bed, and fall sound asleep. That's because the witness character (Cornelia Robson here) in the novel is supposed to be droning about her boring life for a long time, but there are no gaps in her speech to imply that a long time passed - at most there's the waiter bringing a drink at the very beginning who sorta comes out of the blue.
The Tragedy at Marsdon Manor - S3-E6
Plot hole: It is revealed towards the end of the episode that the painting Mrs. Maltravers did when the murder took place was not painted that day and that time of the day, because it had the wrong shadows. But we actually saw what was on the canvas when the secretary was leaving to go to the bank, and it was that exact painting in an early state. She also came up with the idea for the murder the night before, making even more unbelievable that she'd just have the alibi painting ready and waiting the morning after. That without mentioning the fact that the murder itself as described is not something that would have required an amount of time needed to make a whole painting, and that she could have finished it later anyway (she gave it to Hastings a day later, after all).
Double Sin - S2-E6
Continuity mistake: In the car chase, when the woman turns to check the police behind them, the close-up on the steering wheel does not match the position of her hands before and after. Similarly her passenger has the right hand visible when it shouldn't be. (00:28:45)
The Adventure of the Western Star - S2-E9
Continuity mistake: When Lord Yardly is offering wine to Poirot, in the aerial shot Hastings has both hands over the glass, but his hands are in a different position in the consecutive view. (00:20:20)
Plot hole: The whole premise of the plot is that nobody is staying at End House but Nick (and the servants); she even says explicitly that there is just one room that is usable and everyone else stays at the Majestic. During the party though, Freddie tells Maggie to go get her coat which is "in my room." They are at End House, not the hotel, how would Maggie have a room there? (00:35:00)
Plot hole: The killer's plan needs to have Maggie at End House - but it's achieved through Poirot's proposal to have Nick call her to act as added protection. But this makes no sense; Maggie's presence would have not protected Nick in any of the alleged attempts to her life; the frame would have crushed her too, she would have died in the car, she couldn't have prevented the rock from falling, and Nick was shot while the most famous detective was with her, even! A random little girl from Yorkshire would have not mattered, so it makes no sense that Poirot endangered someone for no gain.
Factual error: Poirot has just suffered "a turned ankle", in his words; he's talking with Hastings and the kind woman who helped him out, when their conversation gets perturbed by the noise of a plane. Which is surprising, since the plane in question is a Volmer VJ .22 Sportsman, a plane from the 50s, way after the 1930s setting of the episodes. (00:06:40)
Factual error: Poirot is cycling through Wimbledon; he passes by a house which has a definitely non-1930 car in the yard, and a yellow alarm box on the first floor. (00:18:20)
Audio problem: In the very first turn of Monopoly shown, the player scores 11, but moves just 7 ticks. In the second, a 9 produces 8 ticks. (00:01:40)
Suggested correction: It is entirely plausible that a player does not tap the piece to the board with every move. Sometimes, you tap it hard enough to make a sound; sometimes, you just hover the piece over the square.
Other mistake: This adaptation opens with a nice fake Pathe Gazette news reel. The voice says that "last year" Farley sold a record 5 million pies, and that the new wing of the plant is due to open. At the inauguration, there's a banner behind him saying "1885-1935" and he's saying that in 1935 they sold more pies than at any point in their history, and he gives the kind of speech you give at the beginning of a year, trying to set a new record while still on the hot trail of the previous. At the same time, Miss Lemon tells Hastings that the typewriter broke 'last Easter' and she burst out with Poirot that she has been complaining 'for the last six months', which would put the event at the end of the year.
Plot hole: In the original novel, the victim's voice is described as "shrill." In here, it's quite the opposite. When the trick for the alibi is performed, the relevant lines are not read by John Normington, thus Poirot's exposition at the end, with the girl providing the voiceover, indirectly further exposes its unbelievability.
Four and Twenty Blackbirds - S1-E4
Factual error: Great accuracy went into the dates of this episode - Hastings is following the outcome of the so called "Verity's Match", the 2nd test of the 1934 Ashes series, Australia vs England. The events then should happen between the 22nd and the 25th of June, 1934, compatible with the murder happening on the 16th, and being discovered 3 days after. This however puts it a year before "Murder in the Mews", previous episode where Poirot's dentist was referenced, and that happened in 1935 as stated in the letter to the Chinese laundry.
Revealing mistake: Towards the end of the preliminary murder scene inspection, look at the victim in the last close-up, following the part when Poirot picks up paper from the basket. Specifically, the gun hand: the pinky finger of the supposedly dead person, after being too long in the unnatural position, trembles a little. (00:07:30)
Continuity mistake: As the future victim scoffs saying "Must be a great solace to you" to the Tollivers, his hand goes from midair to the teacup between shots. (00:11:30)
Appointment with Death - S11-E4
Continuity mistake: When Nanny Taylor is discovered in the bath and Poirot is leaning over her, her plait is first across her chest and then it is suddenly along her arm. This is most evident in the flash-back scene at the end.
