I have checked the repositories I have problems with (mentioned above):
https://download.postgresql.org/pub/repos/yum/common/redhat/rhel-7-x86_64/
https://cdn.redhat.com/content/dist/rhel/server/7/7Server/x86_64/os
http://mirror.centos.org/centos/7/storage/x86_64/samba-411/
http://mirror.centos.org/centos/7/cloud/x86_64/openstack-queens/
http://mirror.centos.org/centos/7/cloud/x86_64/openstack-rocky/
http://mirror.centos.org/centos/7/cloud/x86_64/openstack-stein/
https://download.fedoraproject.org/pub/epel/8/Everything/x86_64/
All those except the redhat repo have the problem that they an empty string username and password in the pulpcore core_remote table, i.e. they did not get encrypted. They fail each time.
I have also checked the redhat repository and it does have a client_key which is also not encrypted. It’s actually the first RefreshRemote that is failing:
So it looks to me as if the update of the remote is already failing…