On Portainer UI, Is there a way to create an image from running container so that you can clone it later. Following is the docker commit statement for the same.
docker commit --message=“Snapshot of my container” my_container my_container_snapshot:yymmdd
Is it possible for you to try and delete the registry from Portainer and add it back again?
Also what are the logs from the Portainer container? You can see how to get them here: https://www.portainer.io/documentation/faqs/#articleTOC_8