Actually the text elements do not appear somewhere else - they are not transformed although they are children of other (transformed) GUI-elements. Their transformation stays in the coordinate system of the un-instantiated text element.
I tried “text” and “face orientation” options in the material of the un-instantiated text elements - but this does not help.
This was an unimportant side issue at the time I discovered that and my file was not designed to describe this situation. Therefore I did not open a bug.