When I try to create a part in context of another part (in an assembly) or use Convert Entities I receive the following message.

Your selecton is an external reference; because of the current setting, the reference will be automatically broken.

Where is this settings and how I can change it ?

Yesterday everything was just fine and now all of a sudden this error message.

An image and a movie is added if you need to check it out.

A simplified version of the assembly is attached too.

In this assembly, if I try to use Convert Entities to add the same rectangle to the green part, I receive the message.

Any kind of advice is much appreciated.