When updating a Guide's targeting to a completely different URL, you should also update the Redirect URL field if the Redirection option is turned on. You can do it from the Panel or the Chrome Extension.
To update it on the Extension, click on the Guide's name > Settings > Redirect tab.
To update it through the Panel, navigate to the Guides section and click on the settings of the desired Guide.
Then you can find the Redirection section and its URL field at the bottom of the page.
To learn more about this topic, you can check this article.