Buildings via overpass-turbo

Hi. I am experiencing challenges querying buildings on a campus via overpass with

[out:json][timeout:30];
area[name='Cape Peninsula University of Technology (Bellville Campus)']->.a;
(
  (
    // I want all buildings
    way[building](area.a);

    // plus every building:part
    way["building:part"](area.a);
  // and multipolygon relation ¬ to represent buildings with courtyards correctly
    relation["building"]["type"="multipolygon"](area.a);
  );
-
  // excluding buildings with relation type=building role=outline ¬ I want to correct form/height of the part
  (
    // for every way in the input set select the relations of which it is an "outline" member
    rel(bw:"outline")["type"="building"];
    // back to the ways with role "outline"
    way(r:"outline");
  );
);
out body;
>;
out skel qt;

three buildings are not being harvested correctly https://www.openstreetmap.org/relation/12469713, https://www.openstreetmap.org/relation/12442311 and https://www.openstreetmap.org/relation/12445158 are building:parts with a courtyard (multipolygon relation role=inner) that exist within an outline type=building relation which contain the same courtyard. (i.e.: the courtyard is inside a building:part and the role=outer is coming with the query even though I’ve excluded the outline).

I want the form/shape and height of the building:part and not the outline; while being mindful of every other structure on the campus. How do I exclude the relation type=multipolygon role=outer when type=building role=outline already exists for a structure? Have I created the relations incorrectly? Your help is appreciated.