When the Police Commissioner calls a meeting after the humiliating defeat of his police that was broadcast on television, he sits down in front of a large projection screen television that features a Microsoft Windows desktop. The Windows clock at the beginning of the scene displays the time of 10:55. Seconds later it reads 11:10, and by the end of this 2 minute scene, the clock reads 12:53.
When Cheung and his team approach the abandoned police van, the magazine of Cheung's MP5 disappears and then reappears.
Just after the opening shootout, Cheung's MP5 has a flashlight attached under the muzzle. Later, when the police are chasing the bad guys on foot, the flashlight has disappeared.
When Yip is dangling outside the window and the camera looks down, the street is full of pedestrians casually walking or standing around, and there are no police visible. The narrow street is also inconsistent with exterior shots showing a wide open space in front of the building, full of vehicles and people.
During the opening shootout, one of the bad guys is firing out of a window with an AK-47. He then drops down to the street to shoot at a police van which arrives. During this time he clearly runs out of blanks as his gun stops firing, though gunfire sound effects can still be heard.