Parent page attribute not showing all pages

Hi Folks,
When choosing a parent for a new page the Parent page attribute does not show all pages.
What I get is most pages with these pages repeated 2 or even 3 times as I scroll through the list. Top level parents are shown but many children & grandchildren are missing.
Like a lot of other people the parent page attribute isn’t visible at first when creating the page but eventually it’ll pop up when it feels like.
The only way to apply correct parentage is to publish, go back to pages view, find newly created page and reassign parentage via quick edit options. This is a pain.
Using WP 5.4.1 with theme Jolene.
Any tips greatly appreciated.