When Tom is flying during the battle scene near the end, wires that are holding the jet are clearly visible in several shots.
Before Mordred comes to get his sword, Tom finds a way to magnetize it. Afterward, Mordred has a difficult time getting the sword out its sheath, and it tends to "stick" to his armor. However, he later walks down a corridor with it pointed in the air, close enough to a chandelier, and there is no effect. Not only that, he walks past a table that has metal goblets, with his sword close enough to them, and no effect. However, when Tom fights Mordred, they are close enough again to the table of goblets, and this time, the goblets are attracted to the sword.
Hermes states that Christopher Columbus will discover America in 1492. Columbus did not discover America, but rather encountered America.