Crockett, Bowie, and Radin lead a raid to capture some long-range artillery pieces. As they flee back to the Alamo, one of the cannon flips, and comes to rest upside down. The scene switches to a man who has opened a gate of the Alamo (for the returning raiders), who turns back and yells "Doc" to another man. The scene switches back to the raiders, but the cannon is now on its side with its down wheel on top of Bowie.
There is disagreement as to whether Bowie was injured or sick from an unexplained disease while in the Alamo. Regardless, he was confined to a cot or bed. Yet during the movie he is shown as ambulatory until almost near the end of the siege.
At the end of the movie, Sam Houston is told of the approach of the ladies from the Alamo, as if he was nearby during the siege. In fact, Houston was in East Texas, hundreds of miles away, trying to recruit an army to oppose the advance of Santa Anna. It would have taken the women weeks to reach Houston.
When Travis draws the famous "line in the sand," it is raining heavily, yet the sun is shining brightly on the dampened defenders.
In the final battle, when men are firing their flintlock rifles, they seemingly shoot them without sparking when the cock springs forward. But then they could not fire because their frizzens are already forward, giving their cocks (with their flints) nothing to strike and spark. Thus, they seemingly shoot these rifles, without any flash in their pans, and without any muzzle blasts.
In the final battle scenes, the Mexican infantry charges with fixed bayonets. As they run across the battlefield, many of their bayonets can be seen wobbling and flexing with each step of the man carrying them.
As the Texians occupy the Alamo, the chapel is seen in the background with its iconic parapet. The parapet wasn't added to the chapel until after the US Army occupied it in 1846.
When Gen. Santa Ana's cavalry charges toward the Alamo, the tire tracks of the camera truck are visible in front of the horses.
When the Texians enter the Alamo, a scene shows San Antonio in the distance with the San Antonio River between the city and the fort. The river is shown running straight across. In fact, the San Antonio River was u-shaped in the area between the city and the Alamo.
Davy Crockett's name was David Crockett. His nickname seems to have been applied retroactively. The Wikipedia article shows an advertisement for a clipper ship in Coleman's California Line named "David Crockett". The Crockett figure in the ad is also incorrectly shown as unshaven.
Somebody apparently forgot to tell Arthur Hunnicutt to shave his beard. There is no portrait from life of David Crocket with a beard.