The redirect URL is only used when a user enters the waiting room directly (because you have shared the waiting room URL), instead of being redirected to the waiting room by your website’s CrowdHandler integration.
If you are relying on the redirect URL field, make sure you are sending users to a useful URL. If you are sending the user to a URL that then redirects to another URL, this runs the risk of an integration issue that may result in the user being sent back to the queue. Read the article to learn more.