Other mistake: When Sugimura is looking for Kotohiki, he activates his scanner to see if she is nearby. The scanner shows her location, but fails to show either Mitsuko or Kiriyama, who show up quickly after.
Other mistake: After the veterinarian throws blood all over the floor, we see clean spots appear on the floor in the shape of Sebastian's feet as he walks through the blood. Somehow he never has any of it stick to the bottom of his feet (even when he's in the puddle).
Other mistake: When Arnold Schwarzenegger is falling into the river next to the dam it is so obvious that the stunt man is being lowered at high speed on a cable. Not only does he not gain speed whilst falling, he falls at a constant speed and can be seen almost swaying in the wind. (00:30:50)
Other mistake: As the ground team are on their way to the mars base camp, Carrie-Anne Moss' character is also searching for the base camp via a fixed camera on MARS-1. As the camera finds the destroyed camp, the view switches between various angles/viewpoints from around the camp. These views would be impossible to take from the camera(s) on MARS-1.
Other mistake: In the scene where Duncan has been captured by the Watchers and restrained in the upright table, take note of the needle. The camera pans around the Watcher's head and then shows the syringe delivering its contents. Once the dose is fully administered, it can clearly be seen that there is no needle on the end when he holds it down near the Highlander's chest.
Other mistake: During the landing, when Jerry is getting Ethan and Roger out of the shuttle using the escape pole, the two people going out (presumably the stuntmen) look to in fact be jumping out the hatch, instead of just being pushed/thrown by Jerry.
Other mistake: When Fry is looking around for Riddick at the end, she's holding the blue bottle of bugs to light her way. The blue light on her face isn't from the bottle as she holds it, as she's circling around in some cases with the bottle completely behind her, yet her face is still lit up blue.