While fighting in the streets of Rotterdam, Jackie manages to lose both his shoes. He dons a pair of clogs to finish the fight and run away in, but for the rest of the movie he is wearing the original shoes again. In the Hong Kong version, there is a scene explaining this.
At the start of the movie when Jackie and the commandos are attacking the convoy they do a visual survey with special binoculars first. This shows people inside the vehicles via body heat. The Truck that the three scientists are in, shows only the scientists and no drivers. There should have been at least one person in the cab to drive.
When General Sherman views and crumples the paper that was slipped to him ("Your plan worked. Mission Completed."), the close-up is of a hand far younger than Sherman's in the subsequent shot of him smoking the paper in his pipe.
During his fight with Jackie, Ron Smoorenburg's timing was off for one shot, so Jackie got Bradley James Allan to double him for the shot. Only problem was they looked nothing alike, and Smoorenburg's about ten inches taller than Allan.
When Jackie Chan first enters the building in Rotterdam, he quickly changes into a coffee server's uniform. However, later, as he fights on the roof top, he is back into the clothes he was wearing earlier. He clearly didn't change or, for that matter, bring his old clothes with him.
When Jacki runs up the hill on top of the rocks and screams, "Who am I?" you can see a member of the crew underneath the bridge area. When the chopper shot starts to move around you can see him look up at the camera and move back under the bridge trying to hide.
Most of the car chase in Africa is very clearly shot in Rotterdam. In one shot the landmark Erasmus bridge (the bridge on which the final scene is shot) is clearly visible. The part where they drive down some stairs is set in the "Beurs Traverse" also know as the "Koopgoot", also a very well-known location in Rotterdam. Many other characteristic bits of (urban) Dutch scenery can also be seen.
During the chase scene, the rally driver sets the hand brake, then uses the rear wheels to pelt the assailants with rocks. The hand brake locks the rear wheels, however, which would cause them not to spin. Furthermore, the vehicle (a Mitsubishi Lancer Evolution IV) is all-wheel-drive, which would cause the front wheels to spin as well (as is visible in a previous shot).
At the start of the movie, when Jackie and the commandos are attacking the convoy, they do a visual survey with special binoculars first. This shows people inside the vehicles via individual's body heat. If this is the case, there should be certain parts of vehicles that should appear as red, like a truck's engine block which would have five times the human body heat easily. Also friction would cause the tire treads to have some heat as well.
Around 1h21m, when Gen. Sherman (Ed Nelson) swings his cane at Who Am I (Jackie Chan), he misses and spins around a few times. If you pause at just the right moment, the man spinning isn't Ed Nelson but a stunt double.
The goof item below may give away important plot points.
When Morgan attempts to shoot Jackie in the head, the slide on the gun is unlocked, rendering it nonoperational. However, when he cocked the gun, the slide was locked. Earlier, though, Jackie unlocked the slide when handing the gun to Morgan.