When the twins are at the computer in the library, they are seen reading an article about a woman's suicide, and then quickly turn off the computer when the coach enters. When he turns the computer back on, the screen doesn't match the article that they were reading when they turned it off.
Toward the end when she is driving the VW bus away from the school toward the graveyard, the time of day changes. It is dark at the school, then light outside on the road, then goes back and forth to dusk/nighttime when they get to the grave yard.
When Sam is on her bedroom floor, her striped/small floral comforter is on the bed behind her. Then it changes to a yellow and white pattern with large flowers, even though only a few minutes have passed.
When David tells Kate he's going to see Grace you can clearly see outside Kate's Bedroom Window that it's light outside. When David gets to Grace's House it's dark even though Kate mentions earlier in the Movie that Grace lives really close to their house.
The male lead is seen reading an article in the newspaper, the headline of which says "serial killer arrested at pendleton university," but when he reads the headline aloud, he mentions the professor that killed students at Alpine University, which doesn't match the headline from the paper he's reading