Hi @carnegiea, thanks for supplying the b3dm data. I unfortunately haven’t been able to pinpoint the problem based on that, but here is a post that may be useful to you: Programatically select a 3D building
If that doesn’t work, you could send us the original CityGML data to take a look at. I understand it uses a custom ADE and may not be able to be tiled by ion, but examining it may help us understand the problem.