Revealing mistake: During the gang fight, whenever there's a close-up of someone falling on the road it wobbles and bounces giving away it's a rubber mattress. More evident after a guy is launched through a window and another is crushed against the road. (00:19:43)
Revealing mistake: When Egg Shen helps the others escape by using a crossbow-and-winch device, he fires the bolt into a stone. When the bolt digs in, the stone shudders slightly (since its made of wood or plastic, and no fixed part of the floor).
Revealing mistake: During the fight between the two rival Chinese gangs, several of the men wearing black are thrown to the ground in separate shots at differing times. However, each time they land, the asphalt surface beneath them shakes visibly.
Revealing mistake: After Lo Pan jumps over the truck, the dead soldier on the ground is replaced by a very obvious doll.
Revealing mistake: When Lightning makes his appearance in the street fight scene, at the point where his 'lightning rod' impacts, we can see a badly covered explosive charge and ignition cable on the asphalt.
Answer: Because the battle between the Chang Sing and Wing Kong was between them and the truck.
Grumpy Scot