Info drop on an issue I resolved that I found no info online about:
I was working on my navigation system and found that some objects I had marked as Obstacles (high path cost) were being calculated as null areas while others (of the same object) were being properly marked as Obstacles. I found that my Minimum Region setting was too high (project settings → navigation mesh) and not calculating anything for some of these areas. My lower-cost nav mesh had inconsistent space around the objects and led to some being culled and some being calculated. Note: Setting must be adjusted in Project settings and the recast nav data in level.