Could I possibly get a picture of your Navmesh with characters on it?
I’m thinking the issue isn’t collision at all- it’s the navmesh being modified by people being on it. That could be enough to block off travel, and if the other ways around are blocked off as well, the traveling will fail and they will stand still.
To do this you can simply drag people in and press “P” on your keyboard while in the viewport, without starting a simulation. It should light up all walkable areas as green.