UAT Portal Breaks When Copy Production to Sandbox (UAT)

Has anyone done a sandbox instance refresh with portal configured and managed to get portal working?

Currently I tried to run a full copy of production to sandbox, both has portal addon configured, however after the refresh the UAT portal no longer works and I don't seem to find a way to fix it. The UAT site just throws an application error.

I have tried update the website binding for UAT CRM to point to the UAT Portal site.

To me this is a very common scenario and I don't seem to be able to find any reference on the how to.

Thanks.