1. One of your continuous closed air volumes has an overlapping edge that is causing it to not read as a solid. Bake the closedAirVolumes output and do a DupBorder command on the polysurface to see the buggy edge. Rhino's solid operations are buggy. Hopefully McNeel fix this one soon. ...
a closed solid polysurface rather than separate solid closed polysurfaces of rim, an array of blades, and shroud, I have performed boolean union operations on the fan rim and blades, then on that resulting closed polysurface with the fan shroud, forming a one-piece closed solid polysurface. ...