Audio problem: At the end of this episode, Aang tells Katara that forgiveness is the first step you need to begin healing. But if you watch closely, his mouth isn't moving at all when he says this.
The Tales of Ba Sing Se - S2-E15
Audio problem: After Toph deals with the bullies, she explains that she does not care what she looks like. The lip syncing is off. (00:04:09)
Audio problem: When the fire nation guard is hitting the alarm bell, the last hit before the next shot is not heard. (00:09:50)
Answer: The pirates are from the episodes "The Waterbending Scroll" and "The Waterbending Master" (They're the ones Katara stole the scroll from). The traveling musicians are from "The Cave of Two Lovers. The prisoners of war likely refer to the Kyoshi Warriors, the men of the Southern Water Tribe, and possibly Bumi and the other citizens of Omashu.