
(The bug is not unique to Zion, but is much more common than in the Mojave).
Creatures of any kind (human, animal, insect) may get stuck partially or completely within the terra, rendering them unable to move and potentially impossible for the player to damage. Loading a save from before you entered Zion and then loading the save from within Zion will allow you to bypass this problem. Saving inside Zion National Park, quitting the game and trying to reload from that save will cause the game to get stuck at the loading screen. You can still discover these locations, however tick marks on your compass for these locations will not be visible even after discovering them. If you have not found all of the locations in Zion Canyon and leave, the tick marks on your compass indicating undiscovered locations may disappear when you move close to them upon returning to Zion. This appears to be caused by the player not being added to the DLC's player faction and can be fixed on PC by opening the Gamebryo console commands and typing player.AddToFaction xx00b42e 1, replacing "xx" with the Honest Hearts DLC's position in the load order, typically 2. Attacking one will still cause any White Legs in the immediate area to retaliate but the bug will persist throughout the rest of the add-on.
Every White Legs enemy present in the DLC will not be hostile towards the player. A possible location is the yao guai cave to the right of the entrance where a small cliff overlooks the canyon. Some cliffs in Zion may not be properly structured, causing the player to fall through and render the player's movement to a standstill.