After a virtualization issue caused an unscheduled rebooted of production, I found the DR (log-shipping) monitor incorrectly reporting issues.
It seems the linked-server was no longer working, as @@servername returned NULL on Prod.
On Production SP_AddServer failed as the servername was in sys.servers – but not with server_id 0 (as needed for @@servername).
Removing the incorrect entry with SP_DropServer failed as there were remote- connections using it. And SP_DropRemoteLogin failed as there was not a remote users called NULL.
The fix was to remove log-shipping first using the GUI, which was only partially successful. Then manually, by deleting jobs from prod and DR, and truncating system-tables in MSDB starting log_shipping~ (on both servers).
Once log-shipping was cleaned off both machines I could use … EXEC SP_DropServer ‘ProdServer’, ‘droplogins’ followed by EXEC SP_AddServer ‘ProdServer’, LOCAL successfully. Now the server-name was correctly at the top of sys.servers the only task left was to schedule a reboot so Select @@ServerName would pick-up the new value.
After which I could re-configure log-shipping.