MANY more to come... (See also the imdb listand here.)
When Howie walks up to and is in the schoolhouse, the window to the right of the lecturn, as seen from inside the schoolroom, is open. When he walks into the churchyard, it is closed.
The shots of Howie up close to the picture on the wall in his room during Willow's dance. This is a reversal of what was shot. Howie's ring is on his left hand now and the part of his hair is on other side from what we see. This may have been done because a shot of him otherwise would have included the cabinet to the right of the door, making the shot more cluttered. So they shot him from that side and reversed it to make it look right.