Hi, you are creating invalid multipolygon relations. Our wiki has extensive documentation on multipolygon validity.
Outer rings of mp cannot share sides. 
You should just use simple polygons for these type of buildings or use the building:part method where you would draw a polygon around the outside perimeter and then draw the individual sections as building:parts. These are especially for representing buildings in 3 dimensions but can also be used for simpler mapping like this. 