I have a blender model in the picture below
But when I import it to unity it is as shown below
If we zoom in a bit
It seems the cubes are only showing 2 sides of itself and not the full cube? Any ideas?
It seems like some of your (plank) faces have their normals flipped. You can check it in Blender using either the Face orientation or the Normals options from the Viewport Overlay.