(at around 9 mins) During the first sword fight, Jackie's character accidentally impales his opponent, at an angle upward through his back. Upon the camera moving away and then back, the sword is suddenly through his opponent's stomach, completely level.
(at around 31 mins) The elephant is named "Lakshmi", which suggest a female. But "she" has small tusks. In Asian elephants, only males have the tusks.
Meng Yi takes a river from India to China. There is no suitable river. Some flow from Tibet into India, but Tibet was not connected to the Chinese Empire until the much later in the Tang Dynasty.
In is Qin dynasty, but Meng Yi arrives at the Ming-dynasty Great Wall of China. The Qin equivalent was much simpler.
When Meng Yi and Ok Soo fall from the burning carriage off of the cliff and into the water, we later see Meng Yi wading in the water to retrieve her. Had they actually fallen from such great height into such shallow water, they would have both been killed.
(at around 1h 50 mins) In the end of the movie, when Jack closes the book, on the cover it is written "The Mnth" instead of "The Myth". The difference may be hardly noticeable because of the stylized characters.
When Meng Yi picks up the princess in the river, his helmet is floating in the foreground. An open metal helmet should have sunk, especially if it is falling into the water.
(at around 31 mins) While playing with the elephant "Lakshmi", apparently a female elephant, Mallika Sherawat says to it "Good boy, Good boy".