Corrected entry: Duncan says that Connor disappeared "ten years ago to the day." That would make it 1990. But in the television series which this movie follows, Connor and Duncan fight together in the series premiere. That was in 1992.
Corrected entry: In the final battle between Duncan and Kell, they begin in a long hallway on what appears to be, but is not definitely, the ground floor. They repeatedly knock one another over edges and down steps. At one point they are fighting amongst pipes in what might be a sewer. Yet in the final battle scene, even though they have continually fallen down, they are on top of a building on a steel framework, and they are definitely higher than a great number of surrounding buildings.
Correction: There is a break in the fighting between after they fall all the way down, until the final battle scene. They could have easily just climbed up to the platform where they fought.
Corrected entry: When Kell destroys the Sanctuary and kills all the immortals there, nothing out of the ordinary happens, besides the usual quickenings. Later Methos tells us that the Sanctuary was built on Holy Ground, where immortals can never fight. So Kell broke one of the fundamental rules, with no consequences.
Correction: First of all, the line identifying it as Holy Ground was removed from all video releases, probably because of people noticing that. Second of all, one could argue that, since it was actually Watchers running the Sanctuary, there wasn't anything holy about it anymore, so Kell wouldn't have any problem killing there.
Correction: There was no indication that the movie took place in the year 2000. And besides, the producers keep changing the timeline for Highlander.