This bug has been going on for an eternity, for the love of God, fix your damn city duel CTDs, what the hell is the point of even allowing players to have duels in cities if they crash so often? Either get rid of the ability to duel during sieges, or fix it.
Modded or unmodded, in every campaign, with any character, regardless of whatever you do. You will crash if you have a duel in city sieges. How the Hell have you released more games and DLC if you can't fix something so integral?