Wall is not a solid element

Hi, All

please solve my problem.

when i select a wall from revit it’s output is “Solid” (see no-02),
but i select other wall from revit it’s output is a ‘null’ (see no-01)

i can’t understand why?? please help me…

could be an in-place wall??

no, in-place wall, only wall

What does Element.Geometry return for each?

There could be an deformation which doesn’t match causing the discrepancy.