Insert may be cutting fewer or more hosts than needed. The problem may be solved by forcing regeneration, e.g. by moving the insert out and back by a tiny distance in any direction. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
| C# | 
|---|
|  | 
| Visual Basic | 
|---|
|  | 
| Visual C++ | 
|---|
|  |