I’m not sure what’s going. I did some changes on /knowledge-base/ beforehand but I don’t know how that should affect the 3 mentioned pages. I also get the 404 when I click the link to the published pages in the publishing window.
Your first 404 to /knowledge-base/key-features is due to a redirect you have setup.
You’ll want to remove that.
But your primary issue is that you’ve set your folder slug to knowledge-base-categories.
Change that to knowledge-base on the folder and you should be good.