Child pages that are moved to have a different parent page cannot be edited if the parent page's friendly URL is changed.
Steps to Reproduce:
1. Create a new content page "matrix", add a fragment to it and publish it
2. Create a child page "matrix-explanation" to the page created in #1, add a fragment to it, publish it, and configure the friendly url to be /matrix/explanation
3. Create a new content page "matrix-edit" at the same level as "matrix", add a fragment to it and publish
4. Move the child page "matrix-explanation" to be a child of the "matrix-edit" page
5. Delete the "matrix" page.
6. Configure the friendly URL of the "matrix-edit" page to be "/matrix"
7. Try to edit the "matrix-explanation" page
You should be able to edit the page.
A 404 error is thrown.