The young Marquis d'Apcher is wounded on his right arm during the fight with the beast. Later, it is his left arm that is bandaged.
When Mani is raised above the crowd, his tattoos are on the wrong shoulder.
The young woman in the water pit goes from holding a nubby-horned baby goat to holding a lamb (without nubs), then to holding a baby goat again.
When de Fronsac gets out of bed after the nightmare and walks to the window, while hearing the band, he lacks the scars on his chest --- both the bear and arrow scars.
When Chatel is attacked by peasants in the beginning of the movie, he is struck to the right side of his forehead (it is clearly visible, as the wound bleeds profusely). Later in the movie, the bruise and stitches are on the left side.
When Grégoire is shown using pumpkins for target practice, the pumpkins shatter and splash an opaque orange fluid. Pumpkins do not contain such fluid inside them.
In the "final" fighting scene by the ruins, the wire that makes one of the women "fly" is visible when she lands in the leaves.
The metal claw weapons wiggle when struck in some shots, revealing that rubber look-alikes have been substituted for those shots.
At 1:24:01 (Dir. Cut) as de Fronsac enters the front door of the house, the beast is shown stalking him as de Fronsac, unwittingly, closes the door in its face. His horse, which he left outside --- a couple of yards from the door --- is totally unaffected by the presence of the prowling murderous beast. Further evidence of this --- undisturbed, and uneaten --- horse is seen a few minutes later when Jean Roulier (the resident of the house) exits the same door to fetch some wine.
When de Fronsac knocks on the door of Jeanne and Pierre Roulier's home for his clandestine meeting with Marianne (1:23:55 Dir. Cut ) there is a furry paw on the door frame that isn't visible in any of the other shots of the door.
Mani would not have been called a "Mohawk," even by the Chevalier De Fronsac, as this tribe had not yet been granted this official unique name. In French, he would have been called an "Agnier," "Iroquois" or simply "Indien."
Although the movie takes place around 1767, some of the soldiers use muskets fitted with percussion locks during the hunt. Such locks were patented in the first decade of 19th century and came into popular use after the Napoleonic Wars.
At the beginning, Fronsac says the monster will be examined thoroughly in Paris. Everybody, including him, must have forgotten this intention by the time Beauterne arrived, as Beauterne wouldn't have got away with the fake beast if it was examined as planned.
The conspirators sent a letter about their conspiracy and their plans to the Pope. The Pope only sent Sylvia and nobody else, although he would have the authority to stop the Brotherhood.