Swap the location of the buildings until the nav stops trying to hump the walls of a building it cant see in the game. Expensive, but it should work.
The small buildings are especially quirky, but, not all the time. Some of this is due to the node/placement of the "entry" node for that location/building. Which requires a log of your building setup and where you are stuck, compared to the NPC location.
Idk, sometimes it's flawless, and it comes back 5 minutes later to hump the wall of the same building, trying to walk through the wall to get out, or in. The only conclusion I've made is, the nav can't see the walls of the buildings, only the borders of the plot area. So it requires an entry point for the building, and another entry point for the collection /pickup, but sometimes it needs to come back to a known "empty" area with clear line of sight, so it can relate and repath properly.
You can see this if you pause, move to another area, then resume, boss goes back to the waypoints required, and doesn't renav to get there.
AFAICT the nav system adds a bit of 'English' ie random jitter to the navigation path between 2 points as a feature, except for when it routes around a blackspot or mesh location in the Garrison, ie walls, obstacles, etc. Because the Garrison is so modular, the mesh is kind of flawed at times, because that building doesn't exist according to the navigation system as far as I can tell from the routes taken, it just sees empty spots.
One solution would be to record all the stuck errors and aggregate the worst offending areas for improvement, but the bot, or HB doesn't collect analytics like this, because of the multiple inherent privacy issues.
Also, people might be mounted up, which adds to the stuck issues, tauren height issues are also a factor, Temporary blocks, quest objects, etc.