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Audio/visual unsynchronised
When Zedkov is running after John and Meg after the carwash scene, there is a point at which he fires twice, producing two separate muzzle flashes. There is only one gunshot in the audio track.
During the carwash shootout, the car that John and Meg jump into becomes riddled with bullet holes. Whenever the camera angle switches to the more distant view, as they drive off, the bullet holes are gone.
The MP5k and the Beretta PM-12S that the 'Replacements' use fire continuously for long periods (or in bursts many, many times). An MP5 will empty its 30-round magazine in 2.3 seconds on full-automatic fire.
John and Meg swap guns (an HK USP and a Beretta 92FS) inconsistently between shots before, during and after the shoot-out and car chase.
The pictures of John from the photo machine in the arcade and the one on Meg's computer are the same picture.
In the opening scene, John Lee shoots a gangster in the chest, leaving bloody entry holes. As the gangster falls, however, his yellow jacket opens to reveal an unstained green shirt with no bullet holes whatsoever.
After John and Meg escape from Wei's gang, they return to John's hideout, where he treats her dislocated patella - which looks amazingly like the real thing, makeup or no. John pops the kneecap back into place with no difficulty. However, anyone who has ever suffered that particular injury knows that it would be impossible to immediately stand, walk, run and jump as Meg does when the evil-doers subsequently chase them from the apartment. The tissue damage involved takes weeks, if not months, to heal enough to allow that kind of activity.
During the shootout at the arcade, Ryker uses an MP5K in a briefcase. If the briefcase were actually used in this manner, the shooter would most likely end up with a calf-full of lead. The proper technique of employing an MP5K in a briefcase (as taught by the HK International Training Div.) is to hold it with both hands and brace it against the chest/stomach (muzzle toward the target, of course).
The M16 that John picks up in the car wash to use from the creeper is an A2 model, by its adjustable rear sight. The M16A2 has no full-automatic firing mode; at most, it fires 3-round bursts.
Alan's passport is shown to be a British Citizen (GBR) passport. Given the time the film was made and the time the older blue British passports were retired, Alan would have had a Hong Kong (British National Overseas) passport and not a British Citizen one.
When John Lee is about shoot his mark, the scope cover on the front of the scope is not the correct type of cover. Typically, the red buttoned scope cover is used at the rear side of the scope. Butler Creek makes these type of scope covers and the red buttoned one's are designated as "rear scope cover".
The photo negatives hanging in Meg Coburn's darkroom are actually strips of 35mm movie film.
In the final scenes after the shoot out at the end, when Zedkov runs into John and Meg in the stairwell, Chinese characters are clearly visible all over the walls. However, in a few cuts during the confrontation, a two syllable Korean word is clearly painted on the walls. The word is "bah-boh" which loosely translates to "Dummy" in Korean.
After the shootout at the car wash, the last time Zeedo fires his gun, the report of the pistol can clearly be heard well before the flash from the muzzle is seen.
In the alleyway, when John pulls out a pistol for the third time, he shoots a man on a fire escape, but no report from the gun is heard, nor is a flash seen.
When Zedkov is running after John and Meg after the carwash scene, there is a point at which he fires twice, producing two separate muzzle flashes. There is only one gunshot in the audio track.