How do I reset "Edit Web Part" - Unable to re-add webpart?

When I click edit on an item in a list, I get a blank page.

I'm investigating this and discovered that when I go to "Form Web Parts - Default Edit Form" that there are no web parts on that page.

I've attempted to add various web parts to that page, but can't figure out how to re-add the correct webpart in "edit mode"