Even though the court hasn't accepted a case, Roberts has seen enough info to know or have significant doubt about OB being qualified for office.
The mind plays funny tricks on behavior when you try to suppress information.
Or maybe he stumbled simply because people stumble.
It happens to the best of them.
I think you are correct. Roberts stumbled because he new deep in his subconscious that Obama is NOT qualified to be president. That’s what Freud would probably say.