We have not done any changes in the OOTB web.xml. I have provided the servlet details for SSO and PRAuth in the original post (above). Can you please share the same for your web.xml (SSO and PRAuth) so that we can compare?
So glad that you were able to sort this out! Could you share the resolution here and we can mark it as the Correct Answer that way others who may have the same question in the future could use your resolution to solve for themselves?