Deliberate mistake: When Jason throws Freddy to the wall in the burning house, you can see a window on the wall. Now, the distance between the window and the corner of the wall is about five feet. This gives Freddy space enough to hit the wall and not hit the window. However when Jason picks Freddy up you can see the distance has increased to about one feet. It's like they've put in an extra window where there should be a wall instead.