When Erin kills the last of the masked men in the basement, she is drenched with his blood (which is visible in the camera flashes as she stands and looks at him). However, when she goes back upstairs in the next scene, she has much less blood on her and no more blood in her bangs.
When Crispian is leaving and saying goodbye to Erin, in one shot their heads are nearly touching as they lean together. The shot then changes and their heads are far apart and Crispian is standing up straight, not leaning inward.
When Kelly is thrown through the window of the neighbor's house, the actor who lands on the floor in the pile of glass is wearing pants, while Kelly was wearing a skirt as she ran towards the house, and is wearing a skirt again right before the masked killer kills her on the floor.