In a scene in Phil's house toward the end of the movie, Phil is seen to have large and conspicuous perspiration rings in his shirt. A moment later, during the same scene, the rings are no longer there.
When kids are with Harry and he is talking to a man with a knife, their and his position change between the shots.
When Harry's brother falls down the hill, it's obviously a fake sheet of snow as it all lifts off the ground.
In the closing credits, in the listing of the actors who play the "Neighborhood Children," "Children" is misspelled as "Childern."