Visible crew/equipment: When the slaves roll the flaming ball down the hill, we see it strike several Roman soldiers. Look closely, they are actually stuntmen dressed in asbestos suits.
Deliberate mistake: As the Soviet tank starts rolling, the tank commander obviously uses a hidden step to mount the tank. Soviet T-55/T-62 type tanks did not have steps for mounting by the wheels and axles; to mount a rolling tank using the moving wheels or spinning axles would result in the mounter being immediately crushed and killed.
Factual error: Two passengers play a piano/vaudeville routine in the lounge for the officers and passengers. During its initial season (1936) Hindenburg had a lightweight aluminum baby grand piano on board. However, passenger accommodations were expanded over the winter of 1936/37 and the piano was removed. There was no piano aboard Hindenburg on her fatal flight in May 1937.
Factual error: Pierrepoint is depicted as having a London accent. In real life, however, he was from the north of England, and had a Yorkshire accent, which sounds completely different. This is proved in a BBC interview with him, dating from the 1970s.
Factual error: A headline from the Pantagraph (an Illinois newspaper) dated 19 December 2001, is shown in big letters to read, "Latest Florida recount shows Gore won election." In fact, no edition of the Pentagraph has ever featured an article that claimed this. The only time those words appeared in that newspaper was in small print over a letter to the editor dated 5 December 2001.
Other mistake: When the USA soccer world cup team is practicing in New York, on some field in Long Island, in several shots you can see the steeple for Union Avenue Christian Church, which is actually located in Saint Louis, Missouri.
Continuity mistake: Early in the movie when Thomas falls overboard, John Smith ties a rope around his waist (00:02:56) and jumps in after him. Thomas is very far away from the ship (00:03:12). But when the men pull John and Thomas up, John is holding on to the rope with one hand and the end is left dangling (00:03:36). One of the men who pulled them up then coils the rope with a mere two coils (00:03:48), not nearly long enough to have reached Thomas while he was overboard. In the same scene, when we are viewing the men pulling John and Thomas up from above (00:03:38) there is no extra rope at their feet as there should have been for such a long rope.
Factual error: The film strongly implies that John Dudley, the Duke of Northumberland, keeps his head (literally) by converting to Catholicism. In fact, he was executed well before Lady Jane Grey was.
Factual error: Just after the start of the Korean War, McArthur places a map of Korea on the hood of a jeep to explain to a subordinate general his plans to invade Inchon. The map shows the boundary of North and South Korea not along the 38th parallel, which was the border at the time (1950), but along today's DMZ - not established until the Korean armistice was signed in 1953.
Continuity mistake: In the last scene of the movie Eleanor leaves by boat to go back to her castle prison. When we see Henry waving good-bye he is standing right next to a post when we see him from the back, but this post is nowhere when he is shown from the water. (02:08:10)
Factual error: When Lt. Lee shoots down the second Messerschmidt in Italy, you can see it is a twin engine plane.
Factual error: The film is set in 1987 and Eddie ends up in hospital. However the bed we see him on is a fairly modern one with hand controls to raise and lower the bed. Not available in 1987.
Factual error: In a picture from the UN headquarters in New York in the year 2003 you see two German flags. The German Democrativ Republic hasn't existed since 1990. (01:16:04)
Factual error: The movie takes place during the year 1919. Yet before one of the World Series games the stadium announcer requests that everyone stand up to sing "the national anthem". The US did not have a national anthem until the 1930's when Frankin D. Rosevelt signed into law the Star Spangled Banner as the nation anthem.
Suggested correction: According to Ken Burn's "Baseball", Burns and Ward verify that "The Star Spangled Banner" was sung at a baseball game in 1918 to support the efforts of American Troops in WWI- in which players like Ty Cobb, George Sistler, and Christy Mathewson all fought.
The mistake is saying the announcer called it the national anthem, not that they sung "The Star Spangled Banner."
Factual error: A concrete barrier is shown around the White House in the 1960's. This was not put into place until the 1980's.
Revealing mistake: After Jesus saves the woman from being stoned to death, members of the crowd drop their stones, but the stones bounce back up when they hit the ground.
Factual error: The main plot of 'The War Lord' is based on a total fallacy. Chrysagon, a nobleman in eleventh century Normandy, falls in love with Bronwyn. She is betrothed to Marc, a villager on Chrysagon's estate. When Bronwyn and Marc marry Chrysagon claims 'Droit Du Seigneur', a law that a lord is allowed to sleep with a lesser man's wife on their wedding night. It is often asserted, even by some medieval historians, that 'Droit Du Seigneur' was legally enforced in the middle ages, but no reference to the practice has ever been found in any surviving medieval law code, legal text book, or historical source. It is first mentioned in the sixteenth century, and then as a discontinued practice from a barbarous past (like human sacrifice or cannibalism) but the earliest accounts of the custom do not provide any verifiable sources, suggesting that it originated in over-active minds of writers of popular romances.
Continuity mistake: In the scene where we see the room from a wider shot there is no rifle leaning against the barrel. We then get a closer shot of a man talking and there is now a rifle leaning against the barrel.
Factual error: In the opening shot of the movie while our characters are driving down the street in 1951, there is a post-2000, white Toyota Tercel. It's the 2nd car on the left. The car is removed from the next scene. (00:00:50)
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."