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)
Suggested correction: Linthorn saw them in London. He travelled back to the Basilweather estate, and waited for them to slowly make their way there.
Enola and the young Tewkesbury were in London two weeks prior to Enola's forced enrollment in a boarding school where she was supposed to spend her next few years! Furthermore, there is no evidence of Linthorn having seen them.
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)
Suggested correction: The brothers obviously think that Enola's mother is out of her mind; Being the elder brother, Mycroft would immediately have had to take responsibility over Enola. Even if the mother did only go away for a day or two, Enola would still have required a guardian.
The brothers might as well think whatever they want. The UK's laws still mandate an inquest and a coroner's decision.
