Factual error: A crosshead screw is attached to Ivar's frame. (00:11:21)
Continuity mistake: After spotting Lagertha's boats, Torvi points at the boats and lowers her pointing arm. Another shot later and she is still pointing and lowers her arm again.
The Vision - S4-E12
Revealing mistake: Two oarsmen (or rowers) in Ragnar's boat, the first in front of us and the second from the back, pretend to have an oar but have none. (00:38:35)
Continuity mistake: In the shot where Ragnar asks Floki if he can build something to lift the boats over the mountain after Floki says "Everything I do Ragnar, is for you" it then shows Lagatha and than Ragnar points at Floki and Ragnar says "Let's empty the boats." The camera then shows King Harold and you can see Rollo standing behind King Harold when he should be with the French. (00:10:33)
Suggested correction: It is not Rollo.
Factual error: Bjørn is living in a log cabin in the mountains. This logging technique was not common until 2-300 years later.
Continuity mistake: They take away the ropes around his neck. When King Aelle start to hit him, the ropes appear around his neck again, when the shot changes to shortly after the hit, the ropes are gone again. (00:29:00)
The Profit and the Loss - S4-E7
Continuity mistake: While speaking with Wigstan, King Ecbert's left hand is open and slightly pointing at Wigstan. The next shot his hands are clasped in front of his chest.
Continuity mistake: Ragnar is using a shield for target practice, throwing three knives. The positions of the knives as they are thrown into the shield changes between shots.
On the Eve - S4-E19
Continuity mistake: When Torvi shoots the man that was running toward her, the man falls and the arrow is in his chest but in the next shot the arrow disappears. (00:03:22)
The Profit and the Loss - S4-E7
Factual error: When Floki has a vision of Aslaug outside the viking camp along the seine river in France, the vegetation is that of a pine forest and the landscape is that of a mountainous region. There is no such area from the English channel to Paris, which is only flatland. The scene was filmed in Scotland. (00:34:25)
The Vision - S4-E12
Continuity mistake: Shots from inside the boat show all 3 boats without sails, but aerial views and shots from behind the boats shows them with sails. (00:36:30 - 00:38:40)
Audio problem: Rollo's drummer establishing the tempo of the boat rowers is out of sync with the pounding of the drumbeat.
Revealing mistake: Even though the Vikings are rowing their boats at full speed, there are no wakes from the aft nor waves from the bows as the boats plow through the water.
