Hi Michael,
The initial word back from development is that in order for components (including spaces) to be separate out by floor in COBie, the elements themselves need to exist in separate Models. If you can, try copying just a few elements from any floor (other than the one currently being exported) into a new DGN file, move them from their original location in that new file (and perhaps modify as well), then reference that new file into the original DGN and re-export to COBie. Do these copied elements show as belonging to expected floor?
The initial word back from development is that in order for components (including spaces) to be separate out by floor in COBie, the elements themselves need to exist in separate Models. If you can, try copying just a few elements from any floor (other than the one currently being exported) into a new DGN file, move them from their original location in that new file (and perhaps modify as well), then reference that new file into the original DGN and re-export to COBie. Do these copied elements show as belonging to expected floor?