Audio problem: When the CT technician asks John if he'd like some help getting down, John says "Thank you very much", but you can tell that he's not saying anything and that the line is just dubbed in. (True, the camera is facing away from him, but his jaw and face aren't moving at all.)
Audio problem: When Jason dies, he says the line, "But we have to finish the movie." If you pay attention, his mouth isn't moving for the word "but."
Audio problem: While Paul is telling his story to Chato, his lips aren't moving when he says, "My wife and I were settling into a new house" - his mouth is slightly open, then he smiles and shakes his head. (01:10:27)
Audio problem: At the beginning of the movie, a local errand guy delivers a box to Poirot from a gondola. The actor is supposed to be speaking Italian in his first phrase, but he says "Segnor Poirot, lo pesce!" (Mr. Poirot, your fish!), totally off in accent and grammar, obviously from an English-speaking actor poorly faking an Italian accent. Moreover, the box does not contain fish, but turns out a few minutes later to be a box of chocolates. In fact, the Italian version redubs this line entirely and the guy says the equivalent of "Mr. Poirot, your sweets" in a Venetian accent ("Sior Poirot, I suoi dolcetti!").