Multiple instances of elements

[mroop]

If I try to drag more than one link to an existing sub-machine unto a new diagram I get an error.    

The problem is that this is a fundamental requirement for me as my state machines often have more than one instance of a particular sub-machine in different paths through the state machine.  

I managed to get around this by dragging the submachine for the first instance.  To get the subsequent ones I drag the state diagram contained in the sub-machine unto the new diagram.  This looks the same and you can double click on either one to go to that sub-machine diagram.

Is there a technical or UML reason to not have more than one link to an existing sub-machine on a diagram

Thanks   :-/