The second time Troy and Dillon fire together to signal the ship, their beams are going apart. In the next shot watching the beams go into the sky, the beams are intersecting.
When the sheriff and deputies leave to go to the camp, they take the police car and police Blazer parked in front of the police station. The vehicles are taken at the camp and not recovered for some time, yet each view of the police station have both vehicles parked in front.