When the priest is giving trip information to Behmen and Felson he tells them that the Abby is 400 leagues away and roughly 6 days travel. Behmen refers to this with the comment that 300 of those leagues were through rough terrain. A league was considered the distance that a man or horse could walk in one hour or about 3 miles. That means that the Abby was about 1200 miles away and if a man or horse walked 3 miles per hour for 6 days straight with no stopping or resting then they would have walked only 432 miles or about 1/3 the distance. Considering that they would have to take breaks for food, rest, and sleep then that would leave them with about 10 hours a day for walking. That means that they would actually take about 6 weeks, not days, to get there if they traveled every day.
When Behmen and Felson are putting on their helmets before the battle in the beginning of the movie, their chain mail coifs are down around their neck, not under their helmet as they should to protect the neck. Then the command is given and they start running towards the enemy. Once the two lines clash, and the fighting begins, Felson suddenly has his coif on while Behmen still has his down on his back.
The caption reads "The Coast of Styria". Modern Styria - now a province in landlocked Austria - has no coastline at all. Neither did the Medieval Duchy of Steiermark (Styria in English), which did include the northeastern part of the modern state of Slovenia but nonetheless had no connection to the Adriatic Sea during the era depicted in the film.
When Felson fights the altar boy Kay he states "stand and fight like a man you little jackrabbit". The jackrabbit is indigenous to regions of North America not Europe so a crusader in medieval times would be unaware of them.
In the beginning of the movie, a war scene is placed in the middle of a desert with geographical name of Gulf of Edremit. Gulf of Edremit is in West-Northern Anatolia and has a temperate oceanic climate with a rich natural habitat and therefore not a desert. Also it is actually a gulf.
The Crusades were the 11th, 12th and 13th century religious military campaigns; so a bit before the 1330's dates at the start of the movie. For example, the Siege of Tripoli lasted from 1102 until July 12, 1109. Similarly, the Battle of Artah was fought in 1105.
But - the plague referred to in the movie is probably the one in the Early Modern period (1340-1400) where Europe experienced the worst human disaster in its history when the Black Death (also known as the bubonic plague) hit was later. So I guess some artistic freedom was used to place two Crusaders in a time of Plague and Witch-hunting (the witch trials were also in the Early Modern period in a period between the fifteenth and eighteenth centuries).