CSRF token seems to be not generated correctly and the URL to display patron image in Self Check-out screen is failing with Authentication error.
Patron image is not been displayed when the web-based self checkout system is configured to automatically login with this staff login. When a real staff user login credentials are used to initiate the SCO it is working correctly.
I tested the SCO in the current development version. Both the staff user and the normal user had a patron image uploaded.