Sometimes, when I edit the sketch of an exisiting feature, I'm not allowed to pick newreferences. I get the message: "References to additional 3d geometry may not be made; please select again." When I use Sketch>References (as per the help files), it does not allow me to delete existing refs or add new ones.
As far as I know, it only happens when I make a copy of the feature (i.e. mirror command).
So far, I've only come up with two ways to get around it. One is to delete the feature entirely and recreate it--which is not good if the feature is complicated or has children. The other is to use Edit>References to replace one of the exisiting refs with the one I want. But, sometimes I can't spare any of the existing refs.
What's going on? What specifically causes this lockout? I'd like to know so I can avoid it or change my methods.
Thanks, Chris