GN4 recalculates and updates automatic deadlines when you, or other users:

•Save the parent page

•Change the page deadline and save the page.

•Change the edition deadline and save the edition

•Change the element type (only the deadline of that element changes, for all pages where it is linked)

This applies only on elements which do not have manual deadlines. If such element is unlinked or unassigned from any page, automatic deadline is removed.