When Hogarth is roused from his bed by the return of Henrietta who has been robbed, he is shown at first wearing a nightshirt. Only seconds later, when answering the door to Henrietta, he is now wearing a shirt and trousers.
In the confrontation between the wicked lady and the highway man, she shoots him twice with the same pistol without reloading. Since she has a single-barrel muzzle loading pistol, that would be impossible.
When Hogarth confronts Barbara with the handkerchief in the library, he tells her that he found it at the spot where Ned Cotterell was murdered. In fact, it was given to him on the farm by those who had found Cotterell's body.
During the seduction scene with Kit and Caroline, some of the portraits on the walls are obviously 18th century.
When Barbara is being treated for her injuries, the grandfather clock in the room is obviously 18th century.
When Hogarth disturbs the fornicating couples during the wedding feast, someone is heard to say 'Oh god, Hogarth'. None of the actors present are seen to mouth the words.