Continuity mistake: In the scene where Bette Davis has lost her shawl there is a shot of her and Maggie Smith from far away. They talk about the time and in the background Angela Lansbury is drinking. She puts down her glass and leans her head on her hand. Then the shot changes to a close-up of Bette Davis and Maggie Smith and you can see Angela Lansbury in the background, with the glass in her hand, just about to take a drink. (00:55:05)
Continuity mistake: Take a look at the Karnak temple scene when the massive stone block is pushed off the column to kill Linnet. Seconds before the stone falls, the column and parts of the floor beneath are brightly lit by the sun. Also notice that the stone is positioned maybe 2 yards off to the right of the column's centre. When the stone is coming down in the next shot, most of the column (and the ground) is suddenly in the shade. And when the stone hits the ground it is no longer positioned to the right of the column but in front of it. (00:47:40)
Continuity mistake: At the end, when people leave the boat, as seen in the wide shot, the wood plank is at a different distance from the stair's handrail than when Rosalie Otterbourne and Ferguson leave the boat.
Continuity mistake: Inside Pennington's cabin, Poirot finds the document they were looking. He shows it briefly to Race, who is holding a file with a black binding on the right side (so he's holding it the wrong way). George Kennedy shows up in the next shot, and Race is standing there holding the file this time the correct way, and facing the other way after a further cut. (01:38:05)
Continuity mistake: When Mrs. Van Schuyler mentions a "popping sound", David Niven's position is different in the two takes; first his hands touch, then he suddenly has one hand on the armrest. Similarly, when she mentions "an indifferent champagne" her hand is on her embroidery, but she was gesticulating away from it before the cut. It's then Peter Ustinov's turn to be inconsistent; Niven asks "Could it have been a small pistol" etc. and Ustinov is fingering his moustache, but in the next shot he isn't. (01:29:00)
Continuity mistake: Race hears Poirot's morse code and grabs his mighty swordstick; look at his tie. When he's inside Poirot's room, his Royal Green Jackets tie is styled different; in his own room the small end reach approximately the second-to-last red diagonal stripe of the wide part, while in Poirot's room the small end reaches barely the third-to-last stripe. (01:26:40 - 01:27:15)
Continuity mistake: The 'moray eel' on Poirot's plate is shown in close-up. The garnish is on the left side of the plate. In the wide angles though (and at one point Poirot lifts the plate, so we get a good view) the plate is turned differently, the garnish being on the side opposite Poirot's seat. (01:43:00)