Andreyka's final scar shape differs from the one he was actually slitting.
Dutch voice in the soundtrack. When the rage at the village has ended some voice in the track yells "faster, you idiots" in Dutch, but in that war there were no Dutch warriors involved.
One man kills another by throwing a horseshoe into his eye, yet the horseshoe does not penetrate far enough to even pierce the eye-socket, let alone cause a fatal brain injury.
During the bridge ambush, one man starts screaming before an arrow can be heard passing into his arm.
During the bombardment of the town, the cannonballs leave smoke trails and can be seen in mid-flight. A cannonball, once fired, does not leave a smoke trail, nor is it visible to the naked eye.
Alvaro, and Andrei later on, says a few times "Andalusia el dynamite". However dynamite wasn't invented until the 19th century by Alfred Nobel.
One of the Spanish expletives mentioned is wrong both geographically and time-wise. 'Concha tu madre' is a relatively modern regionalism used in Latin America (mainly Mexico) but not in Spain, and would have never been used by a 17th Century Spaniard of obvious Castilian-Aragonese origin as depicted. The term didn't exist in the time frame of the picture.