Revealing mistake: When the protagonist and Uncle Six battle on top of the escalator, Six gets thrown off, landing downstairs. Very much like a pro wrestling Irish whip, it's quite noticeable how the victim is running towards the move before he gets pulled, with a cut to try to hide the lack of any push from the other hand or forceful twist. (00:12:15)
Continuity mistake: Washing Kai's wounds, CG tells him "I need to know more." Fresh blood trickles down her cheek, but has vanished in the following shot. (00:17:30)
Plot hole: CG is worried that if Kai phones her, he might blow her cover. Kai is no suspicious character and it's established that they know each other after the windshield errand. On the other hand, she engaged in a fight with several thugs and the very boss of the Triad who all have seen her, her cover should be pretty much blown already at that point. It's also quite funny how she made sure to meet with the Captain in secluded locations during long jogs, but then kept in her desk police files about the suspects! Some undercover cop.