Open the database, find the parent layout ID’s and edit them in the WP Admin with this URL:
http://duplicator.mamp/wp-admin/admin.php?page=dd_layouts_edit&layout_id=1788&action=edit

Then remove the Child Cell.
This should bring back the List of Layouts, and then you can proceed re-adding a Child Cell.

The issue is usually caused by an Infinite Loop in layouts assigned to each other recursively.