After the countess has asked Stefan to go and get another drink, the glass has blue stains from the drink on it. In the next shot, when Stefan is in the hall, the glass has none of them anymore. When he returns to his wife and the countess, the glass has blue stains again.
At the end of the movie, daylight just appears like a flashlight. What is more, in the shots of the car from outside it's not so light.
When the countess is launched out of the car and impaled, the next shot shows the car stopped on the wrong side of where it crashed.
When Ilona is lying on the bathroom floor, bikini marks are visible. Vampires are not supposed to have tan lines.
When Stefan is hearing the end of Bathory story and Valerie goes up the stairs, shadow can be seen moving in bottom left as if somebody moved.
When Valerie opens the window to the balcony and is scared, it is clearly shown it was Ilona and she could have recognized her easily, yet she says it was "someone".
At the beginning of the movie, the countess Báthory feigns to look at herself in the mirror, but she isn't seen there, as vampires are said not to behold themselves in a mirror. However, at the end of the movie, just before she tells Valerie to go and fetch Stefan, she is visible in the mirror.