Post stops saving, shows as "page can not be found". Images disappearing from Media library

Since a week, blog posts I create save initially, but then get an uh oh error when I try to save. When trying to preview the page (or view from posts or directly the URL) it gets a 404 - Page not found error.
Also, which feels like it might be related, images that I uploaded recently are disappearing from the media library, even after they had been used in the post.
Please help as we need to publish this page quickly and have already retried creating and publishing it successfully three times.
Even though it says “404 -page not found” I can actually open the page in edit mode, just not view it.

Hello @rosiewrose,

Thanks for writing to us.

There might be a few different reasons for this issue, I would suggest you troubleshoot with a few of the common issues before we investigate your settings.

  1. Testing for Plugin Conflict
  2. CSS/JS Customization
  3. Version Compatibility
  4. Disabling Cache
  5. Permalinks

If none of those work, please send your details in a secure note. Please provide the following details

  • WordPress Login URL
  • Admin level username and password

You can find the Secure Note button at the bottom of your posts

Thanks