Audio problem: Right as Duncan leaps into the "chain room" in the final fight, he lets out a light "Ugh!" sound. Then, about 5-10 seconds later, when Duncan surprises Kell and kicks him... Kell makes the EXACT same "Ugh!" sound effect.
Highlander: Endgame (2000)
1 audio problem - chronological order
Directed by: Douglas Aarniokoski
Starring: Christopher Lambert, Adrian Paul, Bruce Payne, Lisa Barbuscia
Continuity mistake: After mowing down all the Immortals during the Sanctuary scene, one Watcher tells another to take their heads because they might be Immortals. You see the Watcher to the left side of the screen and a robed figure to his left about four feet away drawing his sword. Suddenly, that same robed figure is now to the Watcher right side and about two feet away.
Jacob Kell: What you need to understand is that I don't care about the game. I don't care about the rules. I don't even care about these pathetic souls you keep locked away as a barrier to the prize.
Trivia: The character of Manny, one of Kell's posse, is played by Vernon Rieta, who has been Adrian Paul's Hung Gar Kung Fu teacher for years.
Answer: It seems some catastrophic event occurs. This movie follows the continuity of the television show. In one episode Joe Dawson tells Duncan MacLeod the last time it happened was when two immortals fought in a temple at the base of a volcano. He tells him this caused the eruption that consumed Pompeii. But, Dawson also specifies that it's only a legend, and can't be confirmed as actually being THE specific reason for Vesuvius's eruption.