In the scene where Harry (Bruce Willis) is chasing after AJ (Ben Affleck), he fires his gun, which sends a projectile richocheting, hitting AJ in the leg. It shows him jumping around on one leg. The camera pans to Harry for a second and returns to AJ, which shows him jumping on the opposite leg than before.
But, logically, one would hold the wounded leg off of the ground because the pressure of jumping on it would hurt, so he would keep jumping on his good leg.