Runtime baking not working properly (BuildNavMesh())

The tiles are children of a GameObject with a NavMeshSurface component. Everytime a tile is placed, BuildNavMesh is called, but it doesn't seem to update everything, even when making the voxel size smaller.

Each tile is 1x1 unit. It will rarely put a mesh on a 1x1 lone tile, and you can see at the beginning, it ALWAYS waits until 3 or more tiles are down before generating.

Edit: Scaling the tile up to 2x2 makes it generate every time, but why can't it do 1x1?

 

perhaps your NavMesh agent settings need to be tweaked, perhaps its the agent width / radius that needs to be made smaller so that it can generate a mesh even on a 1x1 tile.