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)
Revealing mistake: Towards the end of the film Medea gets shot by an arrow. If you look closely you can see that no arrow is visible in the air, and that it would have to pass through Jason to actually hit her where it does, as he is in the way.
Revealing mistake: After Talos destroys the Argo, Jason swims to the statue of Hera. It is obvious he is in a pool because the water colour has changed, the water is lapping slightly (like a pool and not the ocean) and finally Hera seems to be propped up by something as she isn't moving with the tide.
Revealing mistake: When the arrow hits Medea and Jason pulls it away from her back, she crouches and the prop pad where it was stuck protrudes.
Revealing mistake: When Talos grabs the Argo and sailors start to fall, they disappear in the wide angles, revealing the ship to be a model.
