Other mistake: When Malagant visits the Round Table, he places his sword at his old position but never retrieves it before he leaves.
Suggested correction: Near the start of the film, when Malagant and his men kill villagers and burn the border village, Malagant wields his current distinctive sword with its long serrated edge. So when Malagant places his own old "Knights" sword (all Knights of the Round Table have identical swords) at his past position on the table, Malagant effectively renounces his former seat at King Arthur's Round Table. Prince Malagant has absolutely no intention of retrieving that sword when he exits.