bxl-forever
There was a problem with the building indeed: UrbIS imports from 2013 made a single building for the Palace and the National Library.  I made two buildings out of it and now the Palace has its own building.
+ Fixed several tagging mistakes in this area, such as building=yes on nodes inside a building.

Here is a view of the building right where your note is located.  If the chapel is the part on the right, it is then correct to have it as a node inside the building and not make a building on its own.
https://nl.wikipedia.org/wiki/Paleis_van_Karel_van_Lotharingen#/media/Bestand:Palace_of_Charles_of_Lorraine_1.jpg

That should be correct now.