When Raymond is shot by the crossbow, the arrow that hits him has black feathers on it, but as he falls off his horse the feathers are white.
When Joan first goes up to the stake, she is wearing white shoes. In the shot after that, she is barefoot.
The knight Bertrand shoots with his crossbow just before Raymond is killed already had the arrow sticking out of his chest in the previous shot.
When Bertrand is shot in the neck at Paris, the number of arrows stuck in his shield changes between shots.
Near the end of the film, when Jean tells La Hire he's going to look for Cauchon, it's snowing in the shots of Jean but not when they show La Hire.
La Hire tells Joan that he fought at the battle of Agincourt, but La Hire did not fight for the French until 1418, three years after the battle of Agincourt.
Joan was burned on May 30th 1431, but when she is led the fire it's snowing
Cauchon was never appointed archbishop of Rouen, even though that was what he had hoped for, he had to be satisfied with the bishopric of Lisieux.
When Joan is led to the stake, her hands are shackled in front of her. When she stands, back to the stake, her hands are together behind (around) the stake, again shackled, but there is a shot where her hands are re-shackled.
When Raymond shoots the knight on horseback, you can see that the arrow is fastened flat across the knight's chest just before it springs straight out as he is "hit".
When Joan is shot by the arrow at Orleans, as she falls off her horse and tumbles down, her sword sheath bends as if though there is no sword inside it. In the next close-up shot, you can see her sword is back inside.
After Joan has had the arrow taken out of her shoulder, and they stand her up, her sheath is on her right side (she wasn't left-handed) and in the next scene where she rides off, the sheath is on her left side.
Just before Gladsdale is shot full of arrows, the holes can already be seen in his armor.
After examining plague victims, Joan uses flaming alcohol to sterilize her hands. However, the existence of micro-organisms and their connection to disease was not known at that time - in fact, hand-washing did not become common medical practice until 500 years later.
When Joan's brother is married, the camera pulls back from the church and, on both sides of the entrance, there are crowds of villagers. On our left, clear to the back it is easily visible that one of the extras is clicking his lighter and lighting a cigarette. This is 1430 or 1431. Tobacco had not even been "discovered" by Columbus for another 62 years.
As Joan walks home after being caught trying to give a child some bread, a crew member with a black and yellow coat can be seen standing on the right side of the screen.
When we first see the castle and city of Chinon, a white and blue truck can be seen on the left side of the screen.
Joan did not have long hair. It's been well-recorded that she had short hair.
As often happens in low-budget film making, the actors don't bother trying to create authentic personalities. Joan of Arc was an ignorant French peasant girl, but Sobieski makes her sound like Lady Macbeth.