Goal with Sub-Goal structure can't be duplicated

The duplication seems to work for a brief moment but then it turns black and gets deleted(?). As Goals won’t be send to the trash, I can’t say with certainty if the duplicate gets deleted or what happens with it.

I know that there already existed a bug report with the problem of Goals that can’t be duplicated but it was set as “Released”. I guess, there still is an issue with it under certain circumstances.