In Ratchet's compartment Poirot folds the charred note in a handkerchief, in the next scene he removes the charred note from his notebook.
In the final scene at the Wailing Wall, Poirot's white pocket square is on the right side of his jacket due to the image being mirrored. In the previous and following scenes, it's on the correct, left side. Then again on the ferry, another similar instance occurs.
On just about every scene Poirot's goatee has either a different shape or different hair patterns. With prominent gray hairs you easily spot the lack of continuity. This is very strange for a character that supposedly has OCD and such a prominent visual characteristic.
When Poirot is collected at the station, the officer tells him "There's been a murder, sir, right on the bloody Nile." however in the plot of Death on the Nile, the murder occurs while Poirot is already there and acquainted with the suspects. The comment was likely added as a commercial reference this other Christie work ('Death on the Nile') which was made into a lavish film with an all-star cast in 1978 and remade many decades later, as Death on the Nile (2022).
Poirot writes down the words from the burning paper in his notebook. When he returns to the notebook it is clear that the message has been rewritten as the writing is not exactly the same.
The rescue crew is equipped only with hand tools, yet they are somehow able to re-rail not just an 82-tonne (180,000 lb) tender but also a locomotive weighing over 131 t (289,000 lb)
Barbital is odorless. Poirot made the determination after sniffing the coffee cup.
Steam engines are powered by steam, generated by burning oil, or in this case coal. Steam is piped to the rail cars to heat them, and is expanded to run a generator and produce electricity. It can be seen that the cars are warm and the lights are on, therefore indicating the steam engine is under fire and producing steam. However, all shots of the steam engine show it with snow stuck to the boiler indicating the boiler is at or below freezing. Furthermore, the engine appears to be knocked off the tracks, which would result in the crown sheet of the boiler becoming uncovered of water and causing the boiler to potentially explode.
Although the steam locomotive shown in the film is an European model, its added effects and features only occur in US locomotives and it would hardly be found in a European locomotive: the sound of the whistle, the bell, the snowplow (seems more like a cowcatcher)
When the train first pulls out of Istanbul, it is shown from an airshot exiting the covered station at what is like a high / full speed: no locomotive could get up enough head of steam to so speed so soon, let alone would do so on exiting where a platform still extends.
Poirot solves a mystery of a theft in the Church of the Holy Sepulchre, announcing his solution in front of the Wailing Wall in Jerusalem. Immediately after this, he appears in a port city to travel by boat to Istanbul. Although Jerusalem is landlocked in the desert, he is not supposed to be in Jerusalem, but his travel to the port city (likely Jaffa) is not explicitly shown.
Clearly in one scene an actor is seen lighting his cigarette with a classic 'Zippo' lighter (and casually closing the top). As the story takes place in 1934, it may seem anachronistic for the 'Zippo', however the first Zippos were manufactured in 1932.
In the opening scenes, one character is seen doing what appear to be martial arts kicks and moves that would not have been widespread in the early 1930s. However, he is a famous and accomplished dancer, and the moves look somewhat like ballet moves. Alternatively, he could have traveled enough to have been exposed to the martial arts.
Although most of the movie plays out in winter in the mountains, none of the characters take special precautions with regards to warm clothing, none seem to mind the cold, and none of them have visible breath as they should in such cold environment.
The "ice" on the outside of the cabin windows is exactly identical on every window of the train.
In the opening scene in Jerusalem, the Dome of the Rock is shown covered in shiny gold. Although the golden dome is an instantly recognizable landmark of Jerusalem - in 1934, when the movie takes place, the Dome of the Rock was covered in blackened lead, and was coated gold only in 1959.
As the train leaves Istanbul, a panorama of the city shows the Galata Tower, a cylindrical tower with a distinctive high conical roof; however, although built in by the Genoese in 1348, the roof was destroyed in 1875, and was not restored until renovations which took place in 1965-67. For the intervening period, including during the time-frame of the movie, the tower was flat topped.
The opening scene takes place in 1934 Jerusalem, more exactly next to the Western Wall (also known as the Wailing Wall). There was no yard in front of the Wall until after Israel took over the place in 1967.
There is prominent product placement for Godiva Chocolatier in the film, however they are using the modern logo rather than the more ornate one which would be correct for the 1930s. Separately, although prior to their 1958 opening of a store in Paris, Godiva did not have a presence outside of Belgium, since the Orient Express was operated by a Belgian company (CIWL) and the movie's winter setting facilitates keeping chocolate solid, it is very plausible that Godiva's chocolate could have been shipped in from their factory or brought in by sister train.
McQueen uses the term 'cash cow', which was not coined until the 1960s, 30 years after this movie was set. The correct idiom would have been 'milch cow' (i.e. milk cow), but few today would understand that term.
Between Vinkovci (last stop before the murder) and Brod (today Slavonski Brod, the final stop in the movie) there is roughly 70km of a totally flat railroad. Nowhere near the alpine/mountain/snowy setting that it is depicted in the movie.
On the train station in Brod, Poirot is talking to two policemen of color, which makes no sense for 1930s Yugoslavia.
Hercule Poirot presents a mystery he had to solve that took place in a church. In his words to the public who came to see him in front of the Western Wall, he mentions that the church is The Church of the Holy Sepulchre, that he claims to be, in his words, "just above them". Well, the Church of the Holy Sepulchre is indeed in the Old City of Jerusalem, but in another part of it: In the Christian Quarter. Above the place where he stands there's, in fact, a different holy place: the Dome of the Rock, but that's an Islamic shrine - not a church.
At around 00:05:30, when Poirot summons a policeman to go to the South Gate in Old City Jerusalem, he actually points to the North (turning his back at the Western Wall and extending his right arm). The officer subsequently follows the direction physically given by Poirot, heading to the North, but not to the South, as intended.
During the effort to find a berth on the Orient Express, attendant Pierre Paul Michel stated passengers already booked all First & Second Classe berths or seats, respectively. Second class passengers would have a separate car from the first class passengers. The train pulled only four cars: a baggage, sleeping, dining, and bar car. During the transit and after the train stopped the film neither shows a second class passengers nor do the characters refer to them, ever.
Poirot wears an elaborate mustache protector the first night on the train. The second night, however, he doesn't, which is out of character, seeing as how he psychologically needs everything to be perfect.
Hercule Poirot is a French-speaking Belgian detective, but the Northern Ireland-born and England-reared Kenneth Branagh repeatedly mispronounces "oeufs", which means "eggs".
After Caroline Hubbard has her conversation with Edward Ratchett in the corridor, she passes Masterman, excusing herself and calling him by name; Masterman replies in kind, calling her by her name. As part of the plan, they have never met before and should not know each other or the other's name.