Hi,
Could it be that Dynamo is having problems getting the solids of elements with openings/voids in it ?
I often have problems grabbing the solids of elements like the above.
Removing the openings/voids from the elements kind of solved these problems and gave me solids (not the correct ones of course).
Maybe Dynamo is having problems to determine the facing orientation of the opening/void faces. In simple words what is the inside and outside of the opening/void faces. The explanation of @jacob.small in this topic Generic Element to Solid Geometry brought me to this thought. I’m not a programmer at all, so i could be totally wrong here 
A few examples of similar topics:
https://forum.dynamobim.com/t/element-geometry-operation-failed/5241?u=mjb-online
https://forum.dynamobim.com/t/generic-element-to-solid-geometry/39971?u=mjb-online
https://forum.dynamobim.com/t/solid-not-a-solid/39904?u=mjb-online
Kind regards,
Mark