Gaffes

The first time we see Wing take out his cellphone in a bar, he was holding a Nokia 7610. Next, when he calls his girlfriend's number outside her apartment, he is holding a Nokia 6600. Soon after, we see him holding his Nokia 7610 again. Just as he enters his girlfriend's apartment, he is using the Nokia 6600 again. From then on, he just uses the 7610.

Jackie's hair changes lengths throughout the film.

After the bank teller, who was used as a human shield by Joe, is killed, he falls to the ground Moments later, an extreme close-up of Joe firing his gun is shown, yet in the shot you can clearly the bank teller's shoulder in the shot

Leaving aside that anyone on the bus could, and would have taken charge and stopped it, there's no way it's possible for it to have hit so many things and run over so much debris without coming to a stop on its own, even if it did avoid running straight into a building or car that would stop it, which definitely would happen.

At the beginning of the movie, a drunk Police Inspector Chan Kwok-Wing (Jackie Chan) is seen failing to get a taxi. When he is sitting on the street, white crosswalk bars can be seen. Hong Kong uses yellow crosswalk bars.

SDU (Special Duties Unit), basically Hong Kong's Counter-Terrorism and SWAT team, would have been called to raid the thieves hideout whether Inspector Wing called their support or not.

When Chan and his assistant repel down a rope in pursuit of the robber, both their improvised equipment depend on the rope being stretched tight for friction. When the robber disconnects, both of them should free fall. Especially the assistant when Chan also disconnects.

When Sam is shot at the X Games event, as he falls back in slow motion, you can clearly see the squib vest the actor is wearing under his costume.

When we see the police hanging from the ropes from above, the ropes are visibly not under tension, showing that the actors are actually supported by safety lines.

When Frank is in the water surrounded by the rubber ducks you can see the green floating barrier at the top of the screen preventing the ducks from escaping.

When the detective gives Chan his Glock pistol towards the end of the movie, he takes the magazine out and lays it on the table next to the gun. Glock magazines have holes in the back of the magazine so you can see how many rounds are in the magazine, and it is possible to see that this magazine is empty except for the one round visible.

When Jackie confronts the purse snatchers for the second time and grabs one by the collar to pull him back, a crew member's hand is visible pushing on the boys chest to help him fly backward.

When Frank is sliding down the building some sort of friction rig is visible where the rope wraps around the pipe he's using as a brake.

When Sasa is going through Sue's profile in the police database, Sue's build can be seen misspelled as "Silm" instead of "Slim".