(at around 45 mins) During the chase scene, just after Tamara disconnects the coach she was riding from the horses that she is now riding, you see the coach tip forward, roll, and shatter apart. In the next shot, the coach is whole again and lands on the front and shatters for a second time.
(at around 1h 11 mins) The fight on the ship starts out at night but finishes in daylight.
In the opening scene, the baby's umbilical cord disappears.
(at around 31 mins) When Ela Shan, the escaped prisoner, first appears at the bar and sits down to hide, he puts his right hand up to obscure his face with no manacle present; subsequently, when Conan goes to arm wrestle him with his right arm, he has a manacle on his wrist.
(at around 46 mins) During the chase scene when Tamara flees the temple, Conan's sword repeatedly disappears and reappears in between shots as he pursues Remo.
(at around 58 mins) Shortly after Conan kidnaps Tamara, he puts her on the back of his horse with her hands tied behind her back. Riding like this would be impractical to the point of impossible. Assuming she didn't immediately fall off and break her neck, she'd be in unbearable agony within minutes of bouncing around in that position.
Set in a primitive era thousands of years before the rise of the known ancient civilizations, the women have shaved legs and armpits.
(at around 1h 35 mins) In the climax when Khalar Zym and Conan are fighting, Conan hits Zym on his face with the back of his sword and he bleeds. Then Zym is shown with no blood on his face, but in the subsequent scene the blood is back on his face.
(at around 1h 35 mins) During the final battle, Conan's sword is pressed up against his arm yet it doesn't cut him at all.
When Conan and Tamara are waiting for Khalar Zym at the Outpost of Shaipur, the face of Tamara's stand-in can be seen in two blurred shots.
(at around 1h 30 mins) During the fight with Zym, Conan falls backwards onto an obviously rubber rock.
(at around 1h 12 mins) During the fight on the ship, Conan is thrown back onto a raised platform in the cargo hold. When his legs fly up, you can see the rubber soles of the athletic shoes built into his leggings.
(at around 1h 17 mins) When Tamara is ambushed by Zim's men in the forest, she does not notice the first rider until he is only a few yards from her, despite having a very clear line of sight for a few hundred yards in every direction and despite there being no noise louder than birdsong to mask the thundering hooves of a galloping horse. Similarly, the foot soldiers were quite clearly not lying in wait - the trees in the forest are too skinny for them to have hidden behind and there is no other cover around - yet they are upon Tamara within a couple of seconds of the horseman attacking.
(at around 1h 17 mins) With no apparent way of knowing where Conan's ship has laid anchor, and with no way of knowing that Tamara would be on land with Conan and not still aboard the ship, Zim's soldiers nevertheless are able to set up a perfect ambush to try and capture Tamara after she leaves Conan's chamber and wanders through the forest.