For Objects following I have to use a average radius of 250 to avoid issues with AI movement.
For Points you have to use cast to nav to avoid some issues.
This being said one thing i see above is that you may need to sink that wall into the floor more so the nav mesh does not cenerate inside your cube. As for corners I have asked this before and sharp corners can cause issues for AI as well as narow spacing. To rid myself of this I have a movement tracker to see how much im moving every tick and if im stuck for too long i scan for a clear point and use that as a waypoint between the stuck position and the destination area to help the AI free itsself. Also play with your grid sizes to make sure they are not too small. That can cause issues as well.