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.
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.
Continuity mistake: In the beginning, a man who can see into the future puts his hands into a bowl filled with ashes. His hands now are blackened with soot, except for a side-on shot, where his hands are clean, with only a small amount of soot on them.
Continuity mistake: When Jason stabs the hydra, he retrieves his hand and walks away. When the shot changes, he's next to the hydra with his hand extended, and walks away again.
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.
