Use case: Mark a word in editor, use Add Link Menu:
Use content structure to find a page and choose an anchor link there - it works.

Instead use Add Link Menu / Search to find the correct joomla article - Use a search result.
When I choose the link to the joomla article itself, the correct URL appears in the the URL field. But if I choose an anchor link in this article, it doesn´t work. There only appear a link to domain homepage and only this link is gettinig saved.