Factual error: Towards the end when the cavalry uncovers the American flag, it has 50 stars.
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 takes place "somewhere in the South Pacific, 1942", yet the transport plane taking LTJG Braden to Hawaii has post-war markings.
Factual error: Atop the desk in the Captain's stateroom is a model of a 5"/25 wet mount gun. The 5"/25 was designed for, and mounted on, U.S submarines; however, it was not introduced into service until 1944, and this is set at the start of World War 2.
Factual error: In the scene where we see a DC-3 making a air drop over the jungles of "Burma" they fly over the ancient city of Sigiriya (a mountain fortress built around 473AD) which is actually in the country of Sri Lanka.
Factual error: It appeared that, during the engagement with the Serapis, every hit by either ship's guns resulted in an explosion and fire. Unfortunately, explosive shells wouldn't be used on shipboard (aside from bomb vessels) until the next century.