There are two scenes in the movie where a heart is taken out from people's bodies, but it's done so quickly and easily that it's painfully obvious it wasn't done at all.
Mabille's skeleton looks fresh and new when her coffin is opened and it doesn't at all look like it was buried for hundreds of years.
When Alaric seduces and kills a woman in the village, she is shown killed, but she's obviously still breathing.
Maurice approaches his unfinished painting and finishes it in half a minute, but the difference between the two is so big that it's obvious he didn't actually finish it in that short amount of time.
When Alaric retreats through the hall of the house near the end of the movie and Maurice follows after him, there is a moving shadow on the left side of the screen, possibly somebody from the crew.
When the villager with the scythe kills Gaston, he does so properly, swinging and capturing his victim in the curve of the crescent blade. When he kills Chantal, he drags the tip of the blade across her throat, a much less efficient way to use a scythe, defeating the purpose of the curved blade.