Audio problem: When Jack says "Anyway, the conch doesn't count on this side of the island", he is clearly biting his banana and eating it, however the dialouge is heard perfectly clear, even though he is eating.
Audio problem: In the scene where Homer teaches the Nuns to sing the hymn "Amen", it is quite obvious that Sidney Poitier's voice has been dubbed by another singer.
Audio problem: While Marcello Mastroianni is waiting at the station and Sandra Milo's train can be heard arriving off-screen, we hear much whistling by a steam train, but when it finally appears, the train is being hauled by a diesel locomotive. [As a side note/explanation - all sound in Italian movies, including the dialogue, is recorded afterwards, sometimes by different actors, eg. Claudia Cardinale in real life has a regional accent.]
Audio problem: The sounds of the prisoners laughing and bantering about during the 4th of July moonshine scene is obviously a looped soundtrack as the same exact sounds and volume are heard at least four times during this scene.