Continuity mistake: After all the rich people bid on the girls, they cut to an American talking on the phone to someone. A school bus pulls up outside and his kids get up from the table with their school things and head for the bus. A few moments later the bus pulls away, yet you never see the kids get on the bus. The door to the bus is in plain sight at all times and when the bus pulls away you see no other door that they could have used.
Continuity mistake: When Beth is first captured, the gun held by the business man is a single-stack .45 ACP 1911 pistol (evidenced by the magazine at the bottom of the weapon). A few seconds later, when the children are lined up, the gun becomes a Beretta with a standard barrel. A few seconds later, when the silencer is attached, the gun magically has an extended threaded barrel (to allow attachment of the silencer). The silencer that was used obviously screwed on, which would not attach to a standard factory barrel.
Visible crew/equipment: When the rich guy couldn't go through with killing the girl with the chainsaw, after the dogs had basically eaten most of him you can see the green screen in the elevator.
Revealing mistake: When the cannibal torturer is cutting into the leg of the victim, you can see its fake legs made of rubber or other material.
Continuity mistake: When Whitney is talking to Beth after Beth has just got off the phone to her dad just before they leave for Prague, you can see the bags that Whitney is holding keep moving. In one shot, both her handbag and holdall are being held in the middle arm area, but in the next shot, her handbag is around her shoulder and the holdall in her hand.