When John, the tribesman and George are at the top of the bluff, George is sat with his rifle slung across his back as he gestures behind him into the jungle. When he pushed to his feet his rifle is suddenly in his hand. After he jumps and during the swing onto the train, the rifle is absent.
The film mentions that the Force Publique is a European mercenary force and it is depicted as (almost) exclusively white (European). In reality the Force Publique was a native (i.e. black) force commanded by European officers (some regular, some mercenary).
According to documents Rom takes at the port, Lord and Lady Greystoke travel to Africa on the White Star Line's Britannic. While the Britannic (sister ship to the Olympic and Titanic) was an actual ship, it's impossible for the Greystokes to have been passengers at that time. The film is set in the early 1890s - construction on the Britannic began November 1911.
It is possible the filmmakers chose an earlier White Star Liner, also named Britannic, which was built in 1874 and scrapped in 1903, but this ship ran a service between Liverpool and New York during the time the film takes place.
Williams' thumbnail is not long enough to apply the siafu / army ants properly. The nail is used for cutting off the necks. You don't simply squash them.
The movie's end credits include the usual disclaimer about all characters being fictional and having no resemblance to actual characters. But the main antagonist (Capt. Rom) is clearly based on Leon Rom (1859-1924), a Belgian soldier and colonial official who became prominent in the administration of the Congo Free State during the late 19th century, and who died in Brussels many years after the movie is set (1890), and was not eaten by crocodiles.
Jane's former home - that of a missionary - is enormous. No missionary of the time would have a house larger than a third of that.
While having dinner with Jane, Rom mentions that during his last visit to Europe he attended lectures by the King of France and Henry Morton Stanley at Sorbonne University. Although the French monarchy was abolished before Stanley's 1871 voyages, several men from the Bourbon family were regarded as king by die-hard royalists.
The giant group of ostriches consists entirely of males (they all have black and white feathers).
@ about 4 minutes, the group shoots into the fog. Look closely and you can see the Gatling gun is just shaking as the bullets are just hanging and shaking, not being fired.
During the fight scene in the wagon, Tarzan hits the big guy out of the wagon and George looks out the wrong direction.
As would be the case with Black Panther (2018), most of the Africans are pale to the point of looking ill. In this film, with the bundu scenes being shot in England, the British climate, latitude, and limited sunshine is a major factor.
The map of Africa is far from accurate. Among other things, Kenya (which is clearly displayed) did not exist - just Maasai tribal lands abutting Somalia, which covered the horn of Africa. The map shown is clearly from at least a decade ahead of its time.
The fastening system used to attach the railroad tracks to the ties are ones used in modern Europe on concrete ties. It's more likely that simple spikes driven in wooden ties would have been used in the latter part of the 19th century in Africa.
The British Prime Minister is a lookalike for William Gladstone. While Gladstone was in office intermittently from 1868 until 1894, the movie is set in 1889-1890 when he was out of office.
On several occasions we can see wild carrot plants, like in the beginning of the movie where Mr Waltz is picking one. The Daucus carrota, wild carrot, is common in England where the movie was shot. Its not an African plant, most certainly not at the time the film was supposed to happen.
When Jane is taken, Tarzan explains that they can catch the boat because it's travelling slowly upstream. Every scene shows the boat moving against the flow. When they finally catch up, the boat is at an ocean port, which is the farthest downstream any river can flow.
Tarzan's father has a full beard and mustache from being marooned. The first time Tarzan is seen as an adult in the jungle with his gorilla family, he is clean shaven.