Continuity mistake: During the enactment of the Battle of Zama, Maximus rides his horse around a bend with his sword in his left hand. When we cut to close up, it's back in his right. Looking at the left-handed shot in freeze-frame, you can see the frame has been flipped, left-to-right (check the armor). This was probably for continuity reasons. Similarly, Maximus jumps on the horse and his shoulder protector is clearly on his injured left shoulder. However, a few frames later, the protector is on his right shoulder, then it moves yet again back the correct spot, the left shoulder.