Factual error: The opening assault of the movie bears the date October 31, 1914. Poirot's squad attacks the Germans using the cover of gas delivered through canisters. The first documented use of poison gas in warfare was in April of the following year by the Germans, but it possible that the Belgians would attack using non-lethal gas, which they employed starting August of the same year. They wouldn't have the gas masks that they are sporting during the assault, though, including a full headed hood designed by Cluny MacPherson in 1915 (worn by one of the extras that wanders behind Poirot as he takes off his respirator). (00:04:10)
Continuity mistake: Poirot and his brothers in arms are rejoicing after their victorious assault to the bridge. The guy who doubted him gives him a pat on the back. The other soldier switches hands on his rifle, and repeats the switch in the next shot. (00:04:55)
Audio problem: Katherine visits Poirot at the field hospital; the opening line has a loud gulping, most likely dubbed, and then Branagh's voice says "I asked you...not to come" with the second part of the sentence added in dub; his lips don't move. (00:05:45)
Continuity mistake: During Salome's opening performance, after she sings "Where in the devil they're at" Poirot is watching intently Simon and Jackie dance in the crowd. There's a rather remarkable view of Emma Mackey with her leg tossed atop of Armie Hammer's shoulder. In the previous shot though she was visible in the background in a different position. (00:10:25)
Continuity mistake: In the scene with Poirot freaking out about the 7 asymmetrical pastries, in the side view Poirot's water glass is far away from him, past the bottle. It is closer to him, to the other side of the bottle, in the overhead view. (00:12:15)
Continuity mistake: Jackie shows Linnet the engagement ring. Gal Gadot in the view from behind puts her hand on her mouth, and the gesture is repeated in the close-up. (00:12:40)
Continuity mistake: Poirot is admiring the Sphynx. He reaches for his drink; in the wide shot you can see that the yellow bookmark inside his Baedeker's is curled in a loop, but it's perfectly straightened in the close-up. (00:16:45)
Continuity mistake: When Poirot shouts at the ribald kite-flier, he stands up from the chair with his arms close to his body. View from behind, and his arms are wide. (00:17:10)
Continuity mistake: In the transition when Bouc tells his mom that Poirot is his "friend, and he's famous", Euphemia is holding her easel and brush differently between shots. (00:19:15)
Factual error: When Linnet walks to her room never to wake up again, she walks past a newspaper ("Daily Sketch") with the date of Monday, May 17, 1937. Since the cover story is the opening scene in the night club, and the wedding happens exactly six weeks after that scene, the movie has to take place in July at most. However, in the hotel lobby in Aswan, during the introduction of Ms. Van Schuyler and her companion (right after cousin Andrew tells the clerk that "not a soul" must see the telegram), one of the guests is reading issue 700 of the French magazine Candide, which came out only mid-August of the same year. (00:20:30 - 01:00:10)
Continuity mistake: The maid is admiring herself in the mirror with the Tiffany necklace, with an unhealthy dose of self-indulgence. The bulky pendant is supported by her middle finger, and her ring finger in close-up is on her shirt. In the next shot, the ring finger is inside the open shirt. (00:21:30)
Continuity mistake: At the reception, Miss Euphemia Bouc walks with Miss Van Schuyler and Bowers saying that money is the only friend a woman can rely on. Look at her champagne glass, a little more than half full. Her son jumps on the desk of the lobby and nods to her, and her glass filled up some. (00:22:00)
Continuity mistake: At the top of the stairs during the wedding party, Bouc makes a comment about adenoids and flat feet while Gal Gadot waves at the guests and her husband with a theatrical gesture puts her hand under his arm. The same gesture repeats in the next shot as we see the pain of doctor Windlesham. (00:22:45)
Continuity mistake: After greeting Poirot, Linnet scuttles away to go hug a member of her multiethnic family. She hugs him throwing her arm over his, but it is underneath Cousin Andrew Katchadourian's in the second shot. (00:23:20)
Continuity mistake: When Gal Gadot picks up the photo showing the inspirational family photo that Cousin Andrew brought as a gift, she holds the box with picture in a slightly different way in every shot (first it changes the distance between her hands and Cousin Andrew's, then the way the paper is folded against the box or flapping freely). (00:23:40)
Continuity mistake: Simon Doyle during the meeting with the family in the hotel lobby professes his love to his bride. He finishes his declaration walking towards her to kiss her, but you can see before Gal Gadot pulls him for the kiss that his face is not moving even if he is supposedly still finishing the sentence. (00:24:15)
Continuity mistake: After Bouc's exposition about every major character at the wedding party, Linnet and Simon run off in the middle of the dance (you can hear the line "Looking good, Simon!" and they sprint away). They do so in a characteristic way - Simon has to slightly duck to avoid someone's arm - but in the reverse shot the action happens in an entirely different way, and Poirot, who they pass by both times, is dancing with his partner in a different position. (00:25:40)
Continuity mistake: The confetti in Linnet and Simon's hair changes position before and after Jackie makes her entrance at the wedding party. (00:25:55)
Continuity mistake: During the marketplace scene in Aswan, Poirot sits down with Jackie to try to talk her out of her stalking routine. She lets him at her table and sets the sunglasses by the handbag. The glasses are angled towards the bag, but when she mentions her father in another shot the glasses are placed the opposite way. (00:29:55)
Continuity mistake: When the boat approaches the Karnak, look at Salome Otterbourne; she is standing up in the shot from the right of the boat, she is one of the last ones to do that in the shot from the other side. (00:34:45)
