Audio problem: At the beginning, when Zuko says "Look, Uncle!", his mouth doesn't move.
Audio problem: When Dre is leaving Meiying's violin practice in the auditorium there is a long shot of her playing her violin showing her left side as Dre walks to the exit. The notes she is playing are vibrato - varying the pitch of the notes by rapidly pivoting the finger on the strings - but her hand is perfectly still. Even though you can only see part of her hand it is obviously that her playing style doesn't match the notes being played.
Audio problem: After Gru has unveiled his plan to steal the moon, he says,"That's what I'm talkin' 'bout!" The animation of his mouth, however, includes the unpronounced "a" in the word "about." (00:11:35)
Audio problem: When Marmaduke throws the party, a turntable falls on the floor and a needle scratch on a vinyl is heard, but the image shows no tonearm nor needle sliding on the record.
Audio problem: There is a clear lip-sync problem in the boat scene, after Eugene takes out the lanterns.
Audio problem: In the last fight scene in the movie the children's mother slams the female Russian spy with a half-empty (she shakes it first) plastic bottle of bleach. When she finally hits the "spy" the sound effect played is the exact same sound effect that they used when Jackie Chan was slamming the male Russian spy with cast iron skillets.