Child diagram of child element print error

[Kobus]

In the new rtf generator you can document child elements of a element. But it seems that if this child element itself has child elements or diagrams, these don't get printed!  

For example: I've got an use-case which has an activity diagram to explain the flow. One of the activities on this diagram is a sub-activity with it's own activity diagram. The diagram of the sub-activity doesn't get printed!

Is there a way to indicate which element sections to include for child elements? Am I doing something wrong?