Other mistake: Tuba is back home after Rambo completely ruined the dinner at his fiancée's. During the scene, the clock on the wall has all hands still, including the seconds. (01:11:00)
Other mistake: When Tuba argues with Rambo in his room and Cheung can't see him, the calendar on the wall is a June 1986 calendar. While it's not specified how long Joanne and Tuba have been dating and it is hinted by the different clothes in each vignette that they certainly have been going out a while, the events of the movie don't take a whole year (the blackmail that caused Rambo's death is attempted again in a later scene, and Rambo wouldn't just let Tuba alone without visiting him for months). Later in the warehouse fight the calendar shows January 1986.
Other mistake: When Rambo gets killed, the lethal shell comes out of the right barrel, but in the earlier close-up on the villain gloating after maiming Rambo's legs, the right barrel was the one that already fired, smoke coming out of it. (00:32:40)
Other mistake: The gag where Tuba draws a lion that initially seems something else is actually pretty funny, but also obviously impossible since the zoom level of the CCTV camera changes entirely throughout it to be able to show in detail what he's drawing. Also, Sammo Hung's denim jacket always covers his arms all the way to his wrists when he's on camera, but the person sketching in the close-ups shows the sleeves of a khaki shirt. (00:17:40)
