Revealing mistake: When the leading hitman jumps from the balcony you see him land on a rubber mat.
Factual error: During the 31st year of the Avalon's voyage, the ship passes close to the star Arcturus, which is about 37 light years from Earth. Later in the movie, it was stated that the Avalon was moving at around 50% of the speed of light. The ship would not have reached Arcturus in the time allotted.
Factual error: In the first scene where Dr Strange is preparing for surgery he uses improper surgical gowning technique breaking aseptic protocols. Strange puts on a mask after washing his hands, contaminating his clean hands by bringing them in proximity to the non-sterile environment of his face. Surgical masks must be worn before the full washing of hands. Another error is that he inserted his hands all the way through his gown to don gloves. Hands must never leave the sleeves and gloves must be put on with the sleeves still covering.
Plot hole: When the group is walking through the jungle for the 2nd time, they have nothing more than their backpacks and a horse to accompany them. Suddenly we see them rowing down a river on a boat and raft. After making peace with the savages, when they have to let a group member go to get medical help, they have been washed ashore as they have been traveling on a single raft since the canoe was damaged by spear attack. How is it that they had a horse and an Indian guide to send away with their injured man? (01:16:55)
Continuity mistake: When Mrs. Otterton is in Chief Bogo's office holding her family photo with both paws, in the wideshots her purse is hanging in the crook of her left arm, but after a brief shot of Judy, when it cuts to Mrs. Otterton's closeup as she tells Bogo about her two beautiful children her purse is gone, then after another brief shot of Judy the purse is back in its place again in the wideshot.
Factual error: In the movie, we see the Statue of Liberty with its current bluish-green color. The statue only got that color over time, and as it was still being built, it should be its original brown.
Continuity mistake: The doctor starts out carrying a Holland and Holland "Royal" Double Rifle; but when he and Tarzan pursue the train, the doctor loses his H&H rifle in the leap from a cliff. Lo and behold, after they commandeer the train and disembark, the doctor is inexplicably carrying his H&H Double Rifle again. The H&H is not a common rifle, even today, and his chances of just discovering an exact replacement aboard the train is beyond coincidental.
Continuity mistake: Periodically, we see beyond the wall, where it appears to be heavily forested just beyond the wall and a distance beyond. However, once past the wall, the group starts with a cliff down and then it is completely barren, with completely different weather conditions (frequent red rain).
Continuity mistake: When April changes into a school girl's outfit to distract Dr. Stockman's assistant, she grabs a miniskirt and ties it around the skirt that she's already wearing. But we never see her take this particular skirt off. It just magically disappears. She is also wearing pantyhose which suddenly changes to over the knee stockings.
Factual error: The film shows cactus and agave plants in many scenes - those plants were imported from the Americas to Judea 1800 years after Jesus.
Other mistake: When Alice's ship is being chased, she orders her crew heel to port (turn left). Instead, it turns heel to starboard (right).
Continuity mistake: When Batman goes to save Martha, he pulls the wooden box with his gun and throws it at one bad guy. The guy's head hits the wall, leaving blood. Later on, you still can see the dead guy but there is no blood on the wall any more. The blood appears again when Batman is about to finish off the last person who was stabbed and pinned against the wall. (02:17:30 - 02:18:35)