Im having trouble playing sieges, mainly because they cause a CTD. It first happened with me playing Haarad ans assaulting a city west of the northernmost settlement. I re-instaled the mod and then played Isengard but besieging Fangorn with Saruman it crashes. I thought it was Saruman causing the crash somehow so I removed him and then attacked, it still crashed. I thought it was the settlement so I auto-resolved and then besieges another settlement with a different army. It still crashes when I fight on the field.

I have no problem with field battles it's just sieges it seems.