Audio problem: When Tiresias describes Scylla to Odysseus he states, "She lurks in the shadows, hoping to fill her belly." However, when he says, "hoping to fill her belly," his lips don't match what he is saying.
Audio problem: When the men are escaping from the cave, the cyclops yells "Where are you?" and pounds his hands on the ground, but the sounds that are heard don't match him pounding the ground.
Audio problem: The exact same sound of someone yelling "Bring the grain" or "Where would you like these sacks of grain?" can repeatedly be heard inside the Ithacan palace throughout the movie.
Audio problem: In the cyclops' cave, Odysseus tells his men to get the wine so that they can trade it for water, but when he does this, his lips don't move.
Audio problem: When Odysseus signals his men to leave the Trojan horse, he says "Drop the rope" and his lips don't match his dialogue.
Audio problem: When Telemachus comes to Sparta, Menelaus asks "Who is this boy my son brings?". Someone then replies "Telemachus of Ithaca highness" but his lips are out of sync when he says this.
Audio problem: After Hector has challenged Achilles, his lips keep moving but no sound is heard.
Audio problem: Having just captured the pig, the soldier with a knife says "I'll stop your squealing" but his lips don't move.
Audio problem: As the sailors are all running back to the ship from the cyclops' island, Eumaeus yells "What happened?", and his lips do not move.
Audio problem: At the very beginning of the film, when Odysseus is running to his wife at Ithaca, we hear him breathing rapidly. His breaths does not match his mouth.
Audio problem: When Odysseus is in the Trojan horse, he says "King Priam" but his lips don't move.
Audio problem: After the Cyclops finishes drinking wine, he throws the bowl back at Odysseus. In that shot you can hear the sound of it hitting him and falling to the ground. But the bowl doesn't actually hit him until the next shot.
Answer: The Trojan War itself was a decade long, followed by Odysseus' ten-year journey home to Ithaca, so all told he was gone roughly twenty years.