Audio problem: When Darian is playing the piano at the party, her hand movements are not consistent with the piece that is being played.
Continuity mistake: When Nick looks out at Darian, he's wearing a checkered shirt, then when he goes out to talk to her, his shirt changes to striped.
Continuity mistake: On walking into the bedroom from the bathroom, Darian is wearing underwear, but when she removes her gown (viewed from the closet), it has disappeared.
Continuity mistake: In the scene where Darian hits Nick with the pole, she smashes a vase on the table. In the close up shot there's not a candlestick on the table, but in the next shot there's a candlestick there.
Continuity mistake: When Amy discovers the hive while hunting sticks, Adrian/Darien informs her that they are yellow jackets, prone to attack in swarms, but the bees Adrian/Darien introduces into Amy's darkroom are relatively docile honeybees.
Deliberate mistake: It's meant to be a joke, but the way the famous punch scene happens is completely ludicrous. Darian appears to be flying in the air toward Nick to attack him, but there is no explanation of how she is doing this, and the way she was thrown back high in the air a few feet is something a punch can never do unless with inhuman strength. There's not any reason whatsoever that both of these things happen, except to give the viewers a laugh. A gun in this case would have made a whole lot more sense.
Revealing mistake: When Darian is swinging the pole at Nick near the end, it's very painfully obvious that it bends as if it is made of rubber or some other similar substance.