Factual error: The KGB agent hunting Jonathan is carrying a Spanish Campo-Giro pistol. There's no way a KGB agent would carry a foreign sidearm in a Soviet Bloc country, especially one that was phased out of service in the late 1920's.
Revealing mistake: Just before Michael and Ellie get out of his car, a fire extinguisher is seen mounted above the dash. Michael opens the hood and the engine begins smoking. Michael reaches into the car for the extinguisher. You can see through the windshield that he is handed another extinguisher instead of removing the one from its mounted spot. The mounted extinguisher is still visible in its holder. Likely done to preserve pacing so he doesn't have to fumble with the clamps on the mounted one.
Audio problem: When Quatermain and Jesse are fleeing in a stolen truck, they are being chased by people in other vehicles. Even though all the streets are dirt, there are numerous times when the tires of all the vehicles squeal.
Other mistake: Most of the obvious misses and awkward parts of the action in the opening can be attributed to the fact that it is revealed a few minutes later being just a drill. However, it does not make sense on any level. The training makes use of live explosives, and at the same time no gunshots are fired but only grenades, with unrealistic trajectories and range. The 'terrorists' don't use their rifles if not to try and bash the good guys on their skulls. That's quite the subpar training, but the top brass are impressed.
Revealing mistake: During the opening assault, notice that the sandbags of the enemy fortifications are more like fluffy pillows; they are squashed under a single person leaning on the bank, and they wobble and nearly fall over when Carrasco himself brushes the hip against them walking by. (00:04:30)
Character mistake: Morgan Hiller's father is named Stewart (according to the story as well as credits). But in one scene when Morgan and his parents are having dinner, Mrs. Hiller calls him (her husband) "David" one time (instead of Stewart).
Audio problem: Just after Binx shoots Mr. Pyot, Hube says, "Don't touch him!" When Billie Jean bends down, the camera cuts to Hube who reaches for the phone saying, "I'm calling the police," but his lips don't move. (00:18:40)
Continuity mistake: Matt and John Eagle put the alligator in the cage in Chuck Norris' first scene. Both of them are significantly more covered in mud for their close-up that ends the scene, once they have already closed the cage and are taking a breather, compared to the rest of it. (00:09:25)
Visible crew/equipment: Near the beginning, at the start of the big car chase down the hill, there is a guy blocking another guy's vehicle. The blocking car is red and backs up before turning onto another road. The reflection of the entire camera crew is visible in the side of the red car.
Continuity mistake: When the men posing as painters rip off the drug dealers, they place a scaffolding plank to cross to the other building, which they remove from the windows and it falls onto the street. When Chuck Norris enters the apartment it reappears.
Continuity mistake: When Leena walks away from Jack (who just 'guessed' her name) saying "Thank God", her hair is a mess under the hat. It's more neat when the camera angle changes. (00:21:50)
Revealing mistake: After the machine runs over the terminal, killing him, when the camera shows the legs being run over again, it's easy to tell that they're dummy legs.