Audio problem: At one point, I think it's when they arrive at the dead Hydra, Aeetes' Captain (with the brown "bobble-hat" and the moustache) says a line like "Some of you up there....and that way," and is pointing to direct the soldiers. It is very obvious that he is not saying this line and that it was dubbed on afterwards.
Jason and the Argonauts (1963)
1 audio problem - chronological order
Directed by: Don Chaffey
Starring: Laurence Naismith, Gary Raymond, Nancy Kovack, Todd Armstrong
Revealing mistake: After Jason's fight with Acastus, when Medea is telling Jason of the flower which can heal his wound, if you look past Medea you can see a mountain in the distance. On top of the mountain you can see a lighted building of some sort that appears to be a modern structure. (01:15:05)
Zeus: If I had to punish every blasphemy, I would have no followers.