Other mistake: Two mistakes in one scene. Continuity Error: As Dewey's father is dueling with Dewey with a machete, Dewey's father cuts a ladder in half. Later in the same scene, you will notice that the ladder is whole. The second (Revealing Mistake) shows a wire leading up from the barn floor to Dewey's father's bottom half, supporting the effect.
Other mistake: There are two mistakes in one scene. First (Continuity Error): As Dewey and Nate duel with machetes covered with sheaths, Dewey swings back hard, dislodging his sheath, and it goes flying behind him. Note where it lands - behind a barn post. After Dewey cuts his brother in half, the shot shows behind Nate, and you are also facing the front of Dewey. Notice the new position the sheath is in - just behind Dewey instead of behind the barn post. Second (Revealing Mistake): After Nate is cut in half, and the shot shows behind Nate talking to Dewey, notice the wire that leads up from the barn floor supporting Nate's bottom half.