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.
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.
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.