When a man is thrown into the pit of snakes by order of the King, it looks as if the snakes are all constrictors and not of the venomous kind; therefore it is highly unlikely that the man would have died from those snakes biting him.
During the funeral scene, the fjord appears, disappears and reappears between shots.
The priest asks Bjorn who a white haired old woman is and replies "She is the Angel of Death." The priest makes the sign of the cross incorrectly. All Catholics touch their forehead, then their chest, then they cross their arm over the heart to the opposite shoulder before touching the other shoulder. This character (definitely not Catholic) touches his shoulders backwards.
Many of the snakes shown in the pit are constrictors, native to the Americas, which was unknown to Europe until Columbus's voyage, another 700 years in the future from this period.