In the scene where Graham is talking to his son in the grocery store... if you wacth the isle closly you can see them change behind Graham.. first its cereal than it changes to can goods after the shot goes from Graham to his son and then back... Wonder how he moved so quick? and the son stood there
malibude is 100% correct. They were walking then stopped. They changed from the shot of Will Grahm (with cereal behind him) to the shot of the kid. The kid speaks but they don't move at all. When they go back to Will he has canned goods behind him. I have seen this movie many times. It's an obvious slip up.