The SQL Server Network Interface library could not register the Service Principal Name (SPN) but KERBEROS connections are possible

After rebooting the server running Windows Server 2012 and SQL Server 2012 there was are an entry in the error log;

Message
The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/SERVERNAME.DOMAIN.ORG:52163 ] for the SQL Server service. Windows return code: 0x2098, state: 15. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.

But when I run the query:

select auth_scheme from sys.dm_exec_connections

I can see KERBEROS connectins active. How is that possible? When I run setspn -L SQLServiceAccount on the server there are no SPN registered for that SQL instance using the domain SQLServiceAccount.

Thanks