Audio problem: Right before the end credits, as Grave Robber says "But Genco may survive if it undergoes surgery", right as Grave Robber says the word "may", his lips briefly don't match what is being said. (Confirmed in DVD commentary.).
Audio problem: In the Final Jam scene, when Mitchie is singing the lines "Every day and every night, it's all we want to do in life," Caitlin and Shane can be seen mouthing "We rock, we rock, we rock," in the background, but it is not actually being sung. (01:32:05)
Audio problem: Sophie and her boyfriend sing at the beach, he says he likes to smoke and pronounces the word "true" with the camera facing him. Right afterwards there's a side shot and music is heard with no lyrics, but he is mouthing as if singing. Then back to a front shot and now he sings and mouths.