When Nero and Jeff Hale are fighting in the boat, Nero throws the sword to Hale pointing to the ground, but Hale catches it pointing up
When Nero is killed and falls from the boat, he is holding his sword in his right hand. But during the fall, his sword moves to his left hand and is then released to fall into the water. As he impacts the river, the sword has returned to his right hand.
During the fight on the boat, after Nero is fatally stabbed, he has a hole in his shirt and dribbles blood down it, staining it. However, when he falls off the boat, his shirt appears clean and unpunctured.
Alice is portrayed as a blonde. The real Alice Liddell-Hargreaves (1852-1934) had dark hair.
Most of the people being reborn to the surface of the water were naked, but many had some covering creating a visual inconsistency.
At 43:50 as the camera pans to the group at the top of the cliff you can see two crew members walking out of shot.
Nero is presented as a superior fighter. The real Emperor Nero wasn't a fighter.