Other mistake: If you talk to the boy in the Kilika inn, he says, "I'm gonna be a blitzball when I grow up." Obviously, he was meant to say "blitzball player," but it was messed up in the end.
Audio problem: In the scene where Tidus and Yuna are conversing at the Farplane, Yuna says something slightly offensive about Tidus' mother, to which he replies, "Whoa there, that's my mother you're talking about!" Almost immediately after, you hear Yuna say, "oh, I'm sorry," but her mouth doesn't move.