Provider or reseller used 'Custom Error Documents' feature to assign custom error document to the HTTP Error 404 for branded Control Panel website.
However, when accessing non-existing webpage in scope of Provider/reseller branded CP the original, non-customized, error appears in browser, see the example below:
HTTP Status 404 - /pem/docroot/some-non-existing-document.html type Status report message /pem/docroot/some-non-existing-document.html description The requested resource (/pem/docroot/some-non-existing-document.html) is not available. Apache Tomcat/5.5.36
Example of used URL: https://cp.provider.tld/some-non-existing-document.html, where cp.provider.tld is the hostname of the branded Control Panel website.
The 'Custom Error Documents' feature does not work for brands due to specifics of the branded websites' configuration.
The problem is going to be fixed in the future updates to POA in scope of the request POA-80290.