I have tried troubleshooting this a few times. but to explain i am sieging with two armies against a karak with one dwarf 20 stack, this is not the first time warriors of nurgle have been present in battle but is the first time a lord and chosen warriors are present, i have tried various methods including changing the lord out however crashes occur when the main army (Around 7-8 units total of warriors of nurgle) are on the battlefield.