Continuity mistake: Kiefer Sutherland throws the suitcases a few steps in front of the middle of the stairs of the entrance of the house but when someone else picks them up, they are on a side of the stairs and close to them. (00:32:45 - 00:33:40)
Factual error: The movie's final scene spectacularly shows planet Melancholia colliding with the Earth, causing the destruction of the planet and everybody dying. The problem is that, in reality, tidal forces from Melancholia would have at a minimum caused extreme natural disasters when the planet made its first pass of Earth. When it turned around to come back (another mistake in itself considering powerful gravity forces would have been needed to cause the planet to do a 180 to hit the Earth), entering Melancholia's Roche limit would have destroyed all life on Earth before actual impact and may have torn the Earth itself apart before the actual collision.