Deliberate mistake: When the police officer is being ran over the tank you see him falling backwards. When it cuts we see his hat being ran over by the tank. However the way the officer was falling there is no way his hat could have landed under the tank's belt as it does in the next shot. (00:01:55)
Deliberate mistake: After Mina leaves the car in Venice, Sawyer just manages to avoid several obstacles on the way, including a bend in the canal. But in the first scene, where Sawyer swerves the car around, its front should have slipped into the water anyway, considering the speed of the car and the tightness of the street, which makes a sharp L-turn at such close quarters next to impossible. But then the scene jump-cuts, and the car is well past the hazard.
Answer: I haven't read this book of Wilde, but I think alterations were prompted not by copyright issues but because this conveniences the "league" storyline.