Other mistake: When Jason unscrews Talos' heel blood spurts but 1) it never creates a puddle and 2) the blood jet disappears in the wide shots.
Jason and the Argonauts (1963)
1 other mistake
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.