After the first part of family values where you “ambush” the approaching “army”, you get news of more enemies trying to destroy the trebuchet at camp, so you have to run back (because the horse will continually knock you off), and stop the enemies from destroying the trebuchet. But arriving at the camp will have you fighting the first few enemies in front of the trebuchet inbetween the spikes on the outskirts of camp, and in the middle of that entrance, the collision mesh makes you fall into the ground until those enemies are defeated and you move on to the interior.
I had a save right before the quest and tried to reproduce it, and it happened again. Now, for all I know, it could be some files are messed up in my directory, but after validating the files on steam, nothing needed to be reacquired.