After you import a 3D model from a STEP format file (*.ste, *.stp, *.step), AutoCAD Architecture (or any other AutoCAD-based product) may display an error:
Failed to calculate silhouettes of a face.
Modeling Operation Error:
Inconsistent containments on coincident face_face_ints.
This error may be also displayed after each completed orbit and so it can slow down processing of your 3D model (up to tens of seconds).
The solution is to set the system variable DISPSILH in your drawing to 0.
E.g. AutoCAD Architecture templates set the DISPSILH variable to 1. A plain AutoCAD, or AutoCAD launched from an AutoCAD Architecture installation, has the DISPSILH variable set to 0.