Geometry Intersects Gives Empty Lists (3). Why? (In 47, out 44)

You are creating colored roomplans right?

No, i am not.

I am creating some sort of Area plans per apartment.
We use the terms verblijfsruimte [VR] and verblijfsgebied [VG].
A group of VR’s where people can ‘stay,’ which a next to each other, are a VG.
I need to know the area (m²) for this VG. Walls are part of this VG area. In the end i also
want to use a Filled Region (///////).

A living room and a bed room can be part of VR.
A bathroom, bedroom, hallway can NOT be a part of a VR.

In example
The area of a VG containing a living room of 4x5 m², a bedroom of 4x4 m²
and another bedroom of 4x3 m² is ~48.8 m. So that is with the walls (4x0.1)
seperating the VR included.

Basicly i am trying to do the same as this, but with a different approach.

I want to use the solids only to create my curve for the boundary for the Filled Region.

Edit
I got it to work using this approach but on the same place the Solids don’t intersect with the Plane
the Boundary of my Rooms is like this

Hmmz

Edit2
No, nevermind. On my second test this failed. I get the following warning:
Warning: PolyCurve.ByJoinedCurves operation failed.
PolyCurves may be branching
.