Although the action supposedly takes place at the height of Norman power in the 11th century, in the area where the movie is set, indeed throughout western Europe, paganism had been largely eradicated by the end of the 8th century. It is conceivable that tiny, secret cells of druids might have existed in hiding until the 11th century, but certainly not an entire village openly practicing druidism. Druidism itself was wiped out by pre-Christian imperial Rome.
Piet (Woodrow Parfrey)must have only recently received his injury. Watching him moving along with one crutch under his left arm, holding it with his right hand, he places his left foot (the one with the supposed injury) on the ground before using the crutch. Woodrow obviously has no idea how a crutch should be utilised.
When Chrysagon first sees Bronwyn naked in the water, we see a close-up of Rosemary Forsythe in the water. When it cuts to a wide shot of Charlton Heston wading in and helping her to stand, Bronwyn is clearly a different girl, a stand in who has darker hair.
When Chrysagon and his men first sight the tower, it is on the right edge of the peninsula, with the sea inlet also on the right. Yet when they arrive at the tower, it and the water are now on the left.
The action supposedly takes place in Normandy, in land belonging to the Duke of Ghent. However, Normandy was entirely under the rule of its own Duke; Ghent was a separate territory under the Count of Flanders.
The War Lord's hawk is a Harpy Eagle, a species recognizable by its dark eyes and crested head. However, Harpy Eagles are from South America, a continent unknown and unreachable for European people in the Middle Age. So, it's impossible for a Middle Age, European Lord to own a bird that comes from South America.
When Draco returns with reinforcements, he deploys a catapult to take down the siege tower, but it would not be transported on the march like modern artillery. It would be packed as a kit with preformed metal parts, nails, ropes, etc. and then built on site with locally harvested lumber, which means it would not be ready for action right away.
Just after the peasant uses the trumpet rock, one of the riders is seen with a flail (sometimes, incorrectly, called a 'morning star'). The spiky weapon is seen to bounce off his horse's head, revealing it to be somewhat softer than it is supposed to be.