The Debt (2) - S3-E7
Other mistake: At the end when it shows that Xena did kill the "green dragon", you can see his eyes move when the camera pans around his face to show the hair clip in his temple.
Other mistake: Ares says to Xena, "Are mortals so stupid as to believe that Dehok will actually bring them peace? They all get what they deserve. I really don't know why you continue to protect them." The Way this is phrased, "continue to protect them," seems to imply that Xena might not be mortal, yet in "Sacrifice II" he says, "You're the only mortal I know who can do that," which means that she is. Why was he implying earlier that she wasn't?