Other mistake: When Morgan is leaving his house at the beginning, he remembers to put the garlic back on the door. He drops his bag of stakes next to one of the bodies he plans to put in the back of his car. After putting the garlic on the door, he never picks the bag up. In fact, the bag somehow disappears in the process. It's not in the car, as you can see it's empty as he puts in the bodies.
Suggested correction: After he replaces the garlic, he is moving away from the door. There is a cut, and he is walking in the opposite direction away from the garage. There is obviously a time jump between the shots. He undoubtedly put the bag in the front passenger's seat.