When waiting at the marina for the van to leave, the rear passenger tire on Washington's car can be seen as flat or nearly flat with no hubcap. In the chase scene that immediately follows, the tire is no longer flat and has a hubcap.
When Fujiyama holds Jennifer at gunpoint, his revolver abruptly changes from a stainless steel Ruger to a blued Smith and Wesson. (This likely occurred because Frank and Fujiyama appear in the same frame, Frank had been using the Ruger up to this point in the film, and a second Ruger was apparently not available to arm them both; refer to Trivia.)
Though Joe Marshall is apparently fluent in Japanese he incorrectly translates the word "Katana" to mean "Japanese sword". A "nihonto" is a Japanese sword, not a katana. A katana is a special sword used by Samurai, which Marshall should know since he is a Samurai Cop.
After the van explodes, the driver transforms from the olive-skinned and mustachioed Orlando Quijano to an obviously clean-shaven and white stuntman. He looks right at the camera and his lips are not even burned.
Henchmen shoot at Frank during the final showdown, repeatedly hitting a window near him. The broken glass obviously falls from the inside out, revealing that the window is being broken by a stagehand hiding inside.
During the final shootout, Yamashita easily fires his short-barreled shotgun without firmly supporting the weapon with his other hand or bracing the stock against his shoulder. It is obvious that he is using low-powered stunt blanks, as a compact 12-gauge shotgun with full-power ammunition is very difficult to control when fired in this manner.
A gangster shoots at Joe, breaking empty glass bottles positioned in front of a wall and a television. The bottles would not significantly slow down or deflect the bullets; the shots should still impact the TV and wall and leave obvious holes.
Frank hides in a doorway and exchanges gunfire with a gangster during the final showdown. The missed shots should punch holes in the bare light-colored door and walls around Frank, but no holes are seen.
Yamashita and his henchmen stab a character wearing a white tank top. As the dying character rolls over, the too-thin fake blood gradually dyes the garment pale pink, rather than making a sharply-defined dark red stain like real blood (or more sophisticated simulated blood).
It is stated that the van driver cannot speak to police because his lips are burned. However, the stuntman's lips were not visibly burned in the aftermath of the crash, and when the bandaged man's lips are briefly seen a short time later in the hospital room, they do not appear burned either.