Factual error: The Essenes climb Masada bearing the scrolls. Just as Joseph Wiseman is framed solo, a black SUV drives from left-to-right below him on the road.
Revealing mistake: During the scenes involving heavy rocks and boulders rolling, crashing, smashing, launching, etc, it is obvious they are made of lightweight material due to their bouncing off each other, the actors, the sand, etc.
Factual error: During some scenes where cavalry is used by both the Romans and the Zealots, some saddles show stirrups attached, which weren't available until centuries after the events of the Masada siege.
Revealing mistake: After Lentius stabs Silva, the knife blade Lentius used bends and wobbles as it is thrown to the ground.