1. Add page "p1"
2. Add a child-page to "p1": "p1.1"
3. Try to change the type pf "p1" to "Link to URL" >>> Error message occurs as expected.
4. Try to do any edit on the form, for example: change the name of the page from "p1" to something else. Save.
>>> Action gets processed successfully (in terms of the result), but the previous error messages are still displayed and no default success message appears.