After the girl returns from the telephone pole she opens the right door of the car. Before she gets in the car the newspaper is still hanging on the inside of the door window, but in the next shot from inside it is gone.
The writings on the mirror inside the washroom (where the girl gets stuck) keep changing between shots.
After the first time the Girl tapes over the gap in the car window she sees a ghost outside the car, they cut to the inside of the car and the tape over the gap is missing.
The outside temperature is below zero but their breath (water vapor) is never seen.
There is no Route 606 in Pennsylvania.
While in the car the radio announcer says, "The National Weather Service in Harrisburg has issued a Winter Storm Warning for the entire Eastern Seaboard..." There is no National Weather Service bureau located in Harrisburg, Pennsylvania and even if there was they wouldn't issue a storm warning covering the entire Eastern Seaboard.
The weather announcer says "the national weather service in Harrisburg". The national weather service location for PA is in State College, not Harrisburg.
Guy turns the dome light off, claiming the need to conserve the battery. However, the high beams are on throughout the movie.
The time says 5:15 pm, but it is still light out and it is almost Christmas.
When they begin their trip there is no license plate on the rear of the car. Even though the girl loads her suitcase into the trunk and closes the trunk lid, she doesn't notice a thing where the plate should be right in her face.
Multiple shadows cast on the snow by the boy and the girl.
After their car crashes, the guy suggests that the girl operate the car's controls while he tries to push it out of a deep snowbank. However, much of the car is so covered in snow and drifts that it would have been impossible to push it out.
At the gas station, the girl's bag is flat when she goes into the stall but is upright when she comes out.
The coroner truck's license plate is blue with gold text. That plate style was phased out in the 80s and 90s and would've been on normal cars and trucks. Emergency vehicles use municipal white plates with blue text.
The girl finds no room in the car's trunk for her suitcase, so she just dumps the guy's shopping bag - containing the food they will need - onto the car park even though there was plenty of space on the back seat (as the movie shows later on).