Hello Beau Jonckers,
You used a multipolygon to define the area of the private garden.
From the outer perimeter of the garden you have therefore excluded the area of the building.
From the rules of multipolygons the outer and inner areas cannot be matching.
In this case OSMI reports that part of the segments are duplicated.
So I modified the garden perimeter by excluding the building, thus eliminated the multipolygon because it is no longer needed.
See: https://wiki.openstreetmap.org/wiki/Relation:multipolygon
