Hi again. 
The reason you added a layer to this building was wrong. This building, like many other tall (high) buildings are not placed on their footprint. This is the place where the building meets the ground.

Keep an eye on complex buildings. Especial the high rise (multi story) buildings and buildings which shows their sideviews  as well. Check this footage how to map these buildings 
https://www.youtube.com/watch?v=dsfUcslLtVc
https://drive.google.com/file/d/13RTwH7sChRWrG5bIjysF2ripBgh3F5l4/view?usp=sharing 

Best regards and keep mapping