As Caesar sits at his table discussing the Druids, there are two small wooden models of catapults sitting on the table. When the camera is pointed at Caesar, the models are close to the center of the table. However, when looking over Caesar's shoulder at his men, the models are just inches from the edge of the table. This changes back and forth instantly between shots.
As the kids (young Vercingetorix and Epona) walk past the table being prepared for the feast, we see a shot of the people standing around the table. The kids change directions and begin to run instead. The camera then changes to a different angle and suddenly everybody around the table has changed positions, even though the kids just started running from the spot where they were just walking. (some people are on opposite sides now, some appear out of nowhere) This is supposed to be one continuous shot but it is clear to see that this scene was filmed at different times and edited together as one.
When Vercingetorix rides up on his horse to kill the man sitting on the throne, he is holding a large spear in his right hand. The camera changes to an outside view looking inside (with the villagers watching). However, the spear is now in his left hand (you have to look closely through the crowd). The scene cuts back inside and once again he has the spear in his right hand.
As Caesar finishes discussing the Druids, he holds his pen up next to his head with his right hand. The camera angle switches to a rear view of Caesar and suddenly his right hand is down on the table top instead. This change happens instantly between shots.
As the Romans march on Alesia, the various camera shots show they shields worn alternately on their left arm and on their right arm
Gauls were not known to wear horns on their helmets.
The type of armor being used by the Romans is the Lorica Segmentata, which was not introduced until fifty years later, and even then was never in such widespread use.
Stirrups, which were not invented until much later, appear on all the horses.