WordPress 5.8, Plugins installed: Advanced Editor Tools (Gutenburg turned off), WPBakery Page Builder, the theme for Lore KB (all plugins installed except LSVR FAQ and Envato Market). Theme is Lore-Child (part of the Lore KB).

If I go to Knowledge Base and add article, the classic editor starts and if I use “Preview” button, it works fine every time. If I then publish the article, go back in to it via Edit Article and click Preview Changes it will come up 404 page not found, if I close that page, then click Preview Changes again, it works, if I close that page and click Preview Changes again it goes back to 404 page not found, the next time, it works again, repeat over and over.

Articles I imported (they use a post_type of ‘lsvr_kba’ ) all just do 404 page not found when Preview Changes is clicked but otherwise all work fine.

The permalinks look correct, no special items in .htaccess.

Any ideas?