Thanks for the suggestions, checking the selection pane was the right hint.
There were forty plus of these text boxes.

No idea where they came from. I do not have any macros running and they were still visible in safe mode. They were not part of the header.

As to the error messages in the header: These are StyleRef-Fields that reference to the Style "Überschrift". That is the German equivalent of Heading. I placed these StyleRef-Fields using a German word version but now work with an English one. Word seems to not be able to adjust for the translation.


Original Problem has been solved.