Factual error: After the scene where Karen Mok is standing in the empty fighting arena, there is a cut to the city night skyline, with the Moon rising fast as time is fast forwarded. However, all the stars remain stationary... Which is nonsense, because the Moon is revolving around Earth much slower than Earth's own rotation. The Moon's (and the Sun's, obviously) rising and setting is because of the latter, that's why the stars should also be moving along with the Moon.
Continuity mistake: In the scene where Tiger goes to see his master at the beginning of the movie, he passes through a door leading into the compound and the shot there shows he opened only the right half of the door. The next shot shows him approaching the camera while running and also shows the door behind him widely ajar with both doors open.
Continuity mistake: In the scene at the beginning where Simon Yam is telling Karen Mok that the case she is working on is closed, as he holds her shoulder to turn her towards the door in one shot, and her hair is completely at her back behind her shoulders, but as he turns her around and the shot changes, her hair on the left side is seen over her shoulder in front.