if by "internal part" you actuall mean "virtual component", then your VAR is correct, you cannot make a stable drwing of the part. the drawing needs to reference a discrete part and/or assembly file to generate the geometry for the views.
if you are not reffering to a virtual component, then please elaborate on "internal part"
Thanks for your reply.
The internal part means it is created from an assembly with references to other part, my question is why some drawings have no problem, I can open it and see it, and others have problem.