Summary

When the user tries to update an existing page, Confluence displays the below error message.

A page with the title x already exists in this space. Enter a different title for your page.

Environment

Confluence Cloud 

Diagnosis

Below error is displayed when trying to publish a new version of the page:

A page with the title x already exists in this space. Enter a different title for your page.

Cause

Confluence validates if the page title is already in use by another page on the Space. This verification is expected.

However, sometimes this error happens on a page that has a unique title. This is very uncommon, but somehow Confluence validates it wrong. 

Solution

Ask to impersonate a user (to avoid logging your name on the last edited by), and then manually re-type the title. The page will be published without errors.