Fixed.  (Thanks, @RaphaelPasloin)
https://www.openstreetmap.org/relation/17858802

@queerthoughts: The problem with this MP is that it was made of 3 contiguous buildings + 1 remote building. The correct way to do this is to draw a polygon to group the 3 contiguous buildings into a single shape (https://www.openstreetmap.org/way/1340611398) and use that (+ the remote building) into the multipolygon. 😉