When the new Mrs. De Winter first enters the room to do her correspondence, there are three books on the table. An establishing shot shows that the book on the left is labeled "menus", and the one in the center is labeled "addresses". Mrs. de Winter picks up the one on the left, and it is now revealed in a close-up to read "addresses" on the cover.
During the inquest, there are two ink bottles of different forms setting on the desk. Beside the bottle closest to the carafe of water, an ink pen can be seen on the blotter. When Mr. de Winter is called to testify, the bottles swap positions and the ink pen is now found beside the examiner's right elbow.
In the Monte-Carlo Hotel Lounge, the Narrator and Mrs Van Hopper are having coffee. The Narrator's coffee cup, then a newspaper are in her right hand between shots without sufficient time or obvious motion to change them.
At the beginning scene of the inquest, the carafe of water on the desk appears cloudy and there is a short drinking glass in front of it etched with a diamond pattern. When Mr. de Winter is called to testify, the carafe is crystal clear and the drinking glass has been replaced with a taller, plain one.
After the luncheon, de Winter and the Narrator are standing on the steps waving goodbye; Jasper the dog moves from one side of the steps to the other between shots.
At the inquest, when Ben begins to testify, the clock reads 11:48. A few minutes later when Mr. de Winter is recalled, it reads 1:53, but then when Mrs de Winter faints, the clock reads 11:48 once again.
In the outside take of Manderley seen in the scene where the Narrator stares at one window being closed, it's a miniature, as is the 'Mrs Danvers' dummy dressed in black. You can realize this by the motion of the window as it's being closed, not in a continuous way, but by little fast jumps, which look too unreal.
Walking back from the beach, the background moves much more quickly than the characters.
When Mr. and Mrs. de Winter first arrive at Manderley, it begins to rain -- but the sun remains shining whilst it's raining.
When the Narrator and Maxim marry, he gives her a large bunch of flowers. She repeats "Perfectly lovely", but the second time, her lips do not move.
Camera dollying back from Mrs. de Winter sitting on a chair brushes some flowers on a table.
The oath taken by the policeman at the inquest is incorrect. He quietly adds 'So help me God' at the end. These words are not used in the UK.
The large map on the courtroom wall is a map of the Americas. It is grossly implausible that such a map would be on the wall of an English courtroom.
Twice during the movie, Maxim leaves Manderley to travel to London, once by train and another by car. On each occasion, he manages to get back before dark. Manderley is in Cornwall, as far from London as you can get, and even with 21st century roads, cars and trains, that feat would be impossible. This error is copied from the novel.
George is driving on the left-hand side of the road outside Monte Carlo.
Towards the end the 'Northern Lights' are mentioned. It is highly unlikely that this phenomenon would be observed as far south as Cornwall.
When de Winter is showing the honeymoon film, he tells Mrs. de Winter "this is where I set the camera up on the tripod". However, the image they're watching zooms in (this is before the cinematographic image zooms in on the entire film-viewing scene in the movie, itself). Since the camera was on a tripod, it wouldn't have been able to zoom by itself since de Winter was posing with his wife at the time, not adjusting the camera.
The word pamplemousse (French for grapefruit) is incorrectly spelled as 'pamplemouse' in the Princesse Hotel Monte Carlo menu toward the beginning of the film.
When Mrs. Danvers draws open the draperies in Rebecca's room, she tugs very slightly at the draw cord causing the huge drapes to open several feet.
Impossible police procedure: immediately after the inquest, the Chief Constable starts a possible murder inquiry, on his own, taking the chief suspect with him. This error is copied from the novel.