Factual error: The old percussion double barrel shotgun is firing modern shotgun shells, which would never work or fit in that gun, and furthermore are also made of plastic, wrong for the era.
Factual error: At the end of the movie Enola rides a bike on the right side of the street. The shot widens and two horse-drawn buses come into view, also on the right side of the road. The movie is set in exactly 1884 (votation). It became mandatory to drive on the left side of roads in England in 1835 (Highway Act). (01:56:33)
Factual error: The film is set in 1884. The locomotive used in the scene on the platform is engine no. 2857, a GWR 2-8-0 that was built in 1903, 19 years after the film is set. (00:04:35)
Plot hole: Enola and Tewkesbury make an unpremeditated decision to visit the Basilwether estate. This decision was made on the spur of the moment, and no-one knew about it. but when they arrive, Linthorn, who is supposed to be in London looking for Tewkesbury, is waiting in ambush to kill them. (01:32:45 - 01:34:31)
Continuity mistake: When Enola and Tewkesbury approach Basilwether, its lights are on. When they enter, its lights are off. (01:34:30 - 01:35:30)
Factual error: Linthorn meets his end when Enola knocks him off his feet. He hits his temple against a heavy and sharp furniture protrusion. Death must have been instantaneous, but instead, he lives to speak a few words. (01:39:18 - 01:39:55)
Suggested correction: He suffered a serious injury, but didn't die right away. There's no indication death was instantaneous.
Every word of what you said is correct. And that's the mistake! Death must have been instantaneous... that is if there was any. A "head trauma", as medical doctors call it, does not have slow-timed effect. The effects range from dizziness to more severe ones, e.g. loss of consciousness, loss of memory, or death. All of them are instantaneous.
Factual error: Viscount Tewkesbury uses Marquess of Basilwether as a secondary title. However, marquess is two ranks above viscount in British nobility; a secondary title would only be of a lower rank, and the only rank lower than viscount is baron.
Factual error: The film is set in the year 1884. The locomotive used in the platform and later action scene is GWR 2-8-0 no. 2857 - built in 1903, some nineteen years after the film is set. (00:04:35)
Continuity mistake: Enola's mother draws the final line through a set of four lines, which are not visible when Mycroft looks at the wall. (00:07:38)
Continuity mistake: When Sherlock says "those kind of mysteries are always the most satisfying to unpick", he's smirking in the closeup, but in the next wider shot from the side he's looking deadly serious.
Continuity mistake: The school uniforms completely change halfway through the school portion of this movie. It's the whole top white piece of the dress. (01:19:46 - 01:22:29)
Factual error: Mrs. Harrison travels to a random, remote country mansion (kilometers away from any civilization), meets a woman who is not her pupil, forcibly takes her measurements, insults her, and slaps her! Nobody in the right mind would do that because they know they would be murdered, harmed, or handed over to the police for trespassing, assault, and battery. (Such outcomes are recurrently portrayed in Sherlock Holmes stories.) Schoolmistresses did use corporal punishment but only on their pupils and within the bounds of school, where they have relative safety. To make matter worse, Mycroft warns Mrs. Harrison in advance. He describes Enola as "unbroken", "a wild and dangerous woman", "a wild child." (Indeed she is; she beats people during the rest of the film. How did Mrs. Harrison escape unscathed?). (00:11:43 - 00:13:46)
Other mistake: Inspector Lestrade of Scotland Yard says "I'm a close personal friend of Sherlock Holmes" and "he doesn't have an assistant." Both are incorrect. Doctor Watson is renowned for being Holmes' personal friend, assistant, and chronicler. Lestrade has always been a client or rival, never a personal friend. (00:58:06)
Suggested correction: In the novels he doesn't have a sister at all. Every version of Sherlock Holmes modifies the source material somewhat. Might be in this version Watson doesn't exist, or they've not started working together yet. Or indeed Lestrade is simply hyping himself up as a person friend when they're actually rivals.
Which novels? Sherlock novels or Enola novels? In both, Doctor Watson does exist. Yes, the film makers **could** have changed it in the film, but when such a thing happens, there is both the burden of establishing the deviation and justifying it. This film rides the Sherlock Holmes gremlin and uses it to attract viewers; plus, understanding parts of it needs a modicum of Sherlock Holmes preknowledge. As such, it is reasonable to expect it to take its burden of establishing and justifying deviations more seriously.
Plot hole: No sooner than the film begins, Mycroft becomes the legal guardian of Enola; Sherlock accepts it without question. How on Earth did that happen? No coroner would grant a transference of guardianship just because someone's mother stepped out of the house and didn't return for a day or two. (00:11:37)