Continuity mistake: When they arrive on the island of Talos, the bronze giant, Hercules and Hylus find the statues atop huge plinths. In close up, they are looking up at the statue of Talos, then in a wide shot they start to walk towards it across bare rocks, then in close up they are back where they were with plants behind them.
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.
Continuity mistake: When Talos comes after the Argonauts, he reaches his hand through an archway in the rocks. After he withdraws his hand (in Harryhausen stop motion), notice one of the Argonauts wriggling and struggling against the rocks as if still trying to get away - the actor doesn't know what the end shot will be like and is still hamming long after the hand is gone.
Continuity mistake: Talos changes size dramatically at several points in this film. For example, when he picks the Argo up, his head and feet are not much smaller than the whole ship, but when Jason is unscrewing his heel his entire foot doesn't seem much bigger than Jason alone.
Add timeDavid Mercier
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.
Add timeDavid Mercier
Continuity 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.
Continuity mistake: At the start of the final battle with the skeletons, Jason and his companions draw their swords and release the shoulder straps that are holding the scabbards, allowing them to fall. During the close-ups of Jason before the skeletons attack, his scabbard strap is back where it was.