During the raid on the shield generator near the start of the film, we see 4 characters slide across the zip-wires but when they enter the interior there are 5 of them. When they leave, the guards shoot 2 but then 4 are shown running across a walkway. The next shot shows a monitor with 5 people running down a corridor.
When Juan Sánchez Villa-Lobos Ramírez was killed in the prison, he had the Samurai sword with him, and Connor MacLeod ran out of the prison with his other sword. In the final fight, MacLeod has the Samurai again.
Throughout the high-speed subway scene, as the camera cuts back and forth from inside to outside the train, the passengers are flying towards the back of the train yet in one shot the passengers can clearly be seen sitting calmly behind Katana. In the same scene, the door separating the passengers from Katana is open in certain shots and closed in others.
Ramírez walks through modern-day Scotland, yet no one he speaks with is Scottish. The confused actor uses a Cockney accent, the man on the street complimenting Ramírez's clothes has an American accent, and the tailor has an upper-class English accent.
Ramírez admires himself in a wall of monitors just before he is fitted for his new suit. A pedestrian walks between Ramírez and the camera, but doesn't show up on the monitors. This is because the camera is zoomed into Ramirez' position on the sidewalk and it does so from a high angle. The pedestrian complimenting him on his clothes is standing close to the store's window and is simply out of the shot because of the angle.