Revealing mistake: When Lucan draws the ring of dead Dagonet's finger, you can see the finger move and keep its position. (01:14:00)
Revealing mistake: Just before the battle of Maldon, the British spy climbs into the big tree and you can see the tree is fake. The spy isn't actually climbing the tree (by grabbing branches), he's using some kind of ladder. (01:36:55)
Revealing mistake: When Arthur is giving his speech before the last battle, in the background are three radio towers. You never know Arthur might need a radio to find out tomorrow's weather.
Revealing mistake: At the beginning, when the Woads are attacking the Bishop's Carriage, Lancelot is hitting one of the Woads. The sword isn't even touching the Woad.
Revealing mistake: In the shot where Guinevere and Arthur are kneeling over the slain Lancelot after the battle with the Saxons, you can see molded rubber soles on Guinevere's shoes.
Revealing mistake: At the start of the film when the Bishops convoy is ambushed by the Woads Arthur stabs his sword at the ambusher, totally missing but the Woad still falls as if stabbed.
Revealing mistake: Despite at least two days of near blizzard conditions there is never more than a few inches of snow on the ground. The amount of snow we see falling should have left well over a foot of snow.
Answer: I don't think it's supposed to be German. Probably Old Saxon. Could be something like "slahten fiand" - slaughter enemy.