Character mistake: In the scenes in San Diego, all the scenes outside the sub are taking place during daylight hours. Immediately after the crewman relays the message about the mysterious telegraph transmission, the scene shifts to the sub. The commander asks what time it is in Melbourne and is told it is 1500 hours (3PM). But if it were that time in Melbourne, it would be 10PM in San Diego, and thus not during daylight hours. (01:33:30 - 01:38:05)
Revealing mistake: During the chariot race, where the contestants are riding towards the screen, tyre tracks from the camera vehicle are clearly visible imprinted in the sand. (00:20:50)
Continuity mistake: After the boy's Noel-Coward-lookalike father says, 'Et les fruits?', goes into the kitchen, and disappears out of shot, watch the cat on top of the bookcase to the left of the door. Before the boy runs into shot, the cat suddenly changes position and a mysterious lens flare appears on the right of the screen, showing that it's actually two shots edited together.
Continuity mistake: When Rick Nelson tells Angie Dickinson to throw the plant pot through the window to distract the gunmen who threaten John Wayne he seems to have had a hair cut between scenes as his sideburns are halved by the time he reaches the street and grow again later.
Continuity mistake: The escape train stops at a station at which another train has been the site of a massacre. One of the victims of this massacre has his head leaning out of a railway carriage window. As Kenneth More and Lauren Bacall from the escape train walk about the station, he can be seen raising and then lowering his head again as he realises that the 'take' is not complete.
Continuity mistake: It is supposed to be night when Joe slips out of the hotel, but a daytime sky is visible.
Factual error: As Frederick is explaining to his guests how to use their .45 automatics, he fires one round at a near-by vase, shattering it. However, it leaves no bullet hole in the wall directly behind the vase.
Plot hole: When the Allies blow up the airfield they pour gunfire from the backs of the trucks into the tents where the Japanese soldiers are eating. If you watch carefully you will see that the Allied guys in the truck nearest the screen are pouring lead through their comrades in the other truck. Another classic case of 'friendly fire'.
Factual error: Anne Frank received her diary on her birthday, and started writing on it 1 month before she went into hiding. In the movie however, she is presented with the diary on the first she arrives at the hiding place.
Suggested correction: Since this movie is based on actual events and not considered a documentary, then the film-makers are allowed to change things to their liking.
While I feel like this sort-of correction could apply to certain elements of movies based on true stories like dramatized scenes (since there has to be some condensation of time and some elements boosted for drama, which can be chalked up to filmmakers changing things), I think a film based on a true story contradicting a known hard fact like this should 100% count as a mistake. Otherwise, you could just as easily argue that any factual error in any film is invalid because the filmmakers are "allowed to change it."
Factual error: The movie is set in Cardiff but the Transporter Bridge seen at the beginning of the film is really in Newport.
Continuity mistake: The background shots of the Matterhorn show it with a clear sky, then a cloud around it, then a clear sky again. This keeps happening.
Other mistake: When the Behemoth swims up the river & capsizes the ferry, a static model is used that bears no resemblance to the animation model seen throughout the film.
Continuity mistake: When Molly (Sandra Dee) grabs the letters she had hidden in the suitcase under the bed, her dress is still unzipped in the back. After ranting at her mother for having read the letters, she throws them into the fireplace, only now her dress is completely zipped up.
Factual error: The movie takes place "somewhere in the South Pacific, 1942", yet the transport plane taking LTJG Braden to Hawaii has post-war markings.
Factual error: When Mrs. Lane screams at the sight of the horse, on the back of Karen Steele you can see the outline of a modern bra under the shirt. (00:23:30)
Continuity mistake: When Richard Hannay jumps from the Sheriff's window into a passing truck it is full of bales of hay. The next time we see him in the truck it is full of sheep and the bales of hay have vanished.
Other mistake: A police officer fires two shots, hitting a bank robber in the back. The "bullets" do not make holes in the robber's coat. All they do is create two tiny puffs of dust.
Continuity mistake: Susie, a six-year-old girl, leans over a bathtub and reaches for a rubber duck. She falls into the tub but it obvious the tub has no water. (The actress, Terry Burnham, landed on a pad or cushion.) Immediately after she falls, there is a very noticeable jump in the film. Then water splashes up but the splash is much too high to have been made by the little girl. The next scene shows the mother entering the bathroom and the little girl, now completely drenched, standing up in the bathtub.