(In the climax shopping mall set) After Chan is thrown against the metal shelf rack and he falls on the floor for it to fall on top of him; later continuation fight scenes show it back up against the wall.
When Kevin/Jackie is climbing onto the bus using the umbrella, as he reaches around the side of the bus we see the handle of the umbrella is clearly bent, but in the next shot, which looks back to him reaching round side of the bus the handle is back to normal.
During the bus chase in the beginning of the film, when the bus goes down the street with road works the goon holding the knife on the driver is actually holding the knife with the blunt edge against the drivers neck.
At 39:29 - 40:18 you will notice that in between shots the seat belts are on then off.
Throughout the scene where Chu's men attack both Ka Kui and Selena, vehicles clearly marked "The JC Group" (Jackie Chan's stunt team name) are visible.
The car with the faulty hand brake could have simply been stopped by either setting the gearbox to "P" or, in the case of a manual car, engage the first gear.