Continuity mistake: As the girls run from the killer, the one girl is shirtless as she starts to run, holding her shirt in front of herself to cover her chest. The camera changes to a rear view and now she is running with the shirt in her hand swinging wildly. The camera changes again and suddenly she is running and putting her shirt on, already pulled over her head, a major change from the last shot. Finally, the camera angle changes again and she has her shirt on completely. All of her shirt/hand positions change instantly between shots.
Audio problem: When Pete is coming down the steps at the indoor beach party, you hear the DJ say a few words, but if you notice, his lips don't move, nor does he look up, and he keeps spinning the record.
Continuity mistake: After Jenny is done speaking with Lars, she picks up a large platter of food and holds it like a waiter/waitress over her right shoulder. (this is a front view) The camera changes to a rear shot and suddenly she is holding the platter over her left shoulder. The scene switches back and she is once again holding it above her right shoulder. This changes back and forth instantly between shots.
Continuity mistake: When Hank and Yu are killed, Hank has the message "Don't let this be Yu" carved into his chest, however, towards the end, when the killer hangs all the dead bodies up in the clubhouse, Hanks shirt is open, and there is no marks on his chest at all.
Continuity mistake: When Lars startles Jenny from behind she lets a mouthful of her red drink spill out, but when she turns around there are no stains on her clothes and her face is perfectly clean.
Continuity mistake: More blood on Kelly's face appears for no reason in the shot just before she's decapitated. (00:06:45)
Continuity mistake: Hank says the killer is left handed but he always holds the knife with his right hand.
Continuity mistake: Juan's shirt is covered in blood before he breaks the hot tub window. Once the water runs over everyone, his shirt is clean. Later, his shirt is covered in blood again.
Factual error: When Kelly's head gets chopped off from her P.O.V. the killer slices her neck from left to right, and her head spins anti-clockwise, If it was from Left to Right her head should spin in the opposite direction. (00:06:45)
Other mistake: In the scene where the dead bodies are hanging, Pete has "naughty cal" carved in his chest but Carlos, the one who this was written on before doesn't have it anymore.
Revealing mistake: When the crew discovers Coconut Pete's dead body if you take a quick look at him before they cut away you can tell he wasn't really dead because his mouth moves right before they cut away from him.
Other mistake: When Pete is introducing his staff and they are all dancing on stage, there is a beautiful brunette who walks up and dances almost the entire time between Juan and Sam. She is supposed to be part of his staff. Yet out of the blue when the camera pans right before Sam interrupts Pete she disappears. Literally from the entire movie to never be seen or spoken of again. There is not even a name on Sam's activity board for whoever this mystery woman is. (00:10:20 - 00:11:20)