Please note that we've updated the Mount & Blade II: Bannerlord save file system which requires you to take certain steps in order for your save files to be compatible with e1.7.1 and any later updates. You can find the instructions here.
Yep its been there the whole time I've been playing sometimes you get lucky and they'll use one of the three ladders on the seige tower occasionally I've seen them even use two but not often. Other times they mill around or go up then back down again.
I think people just got fed up reporting it and knock down the walls instead