Subscription Manager GUI - unregister deleted system

I have a RHEL 7 system that I deleted from the 'Subscriptions" page in Red Hat customer portal, now I am stuck unregistering/re-registering it in the Subscription Manager GUI on the system itself (can solve it by going to console, but humour me).

The system still thinks it is registered so when I select "System -> Unregister" I am prompted with the following:

Errors were encountered during unregister.
Unit XXXXX-XXXXXX-XXXXXX  has been deleted
Please see /var/log/rhsm/rhsm.log for more information

When I select 'OK' I am dropped back to Subscription Manager GUI and nothing has changed. The log shows a response from the registration server that the system has been deleted, then there is a Traceback. I can't find any way out of this situation using only the GUI.

I was expecting it to ask me to clean up / remove the local (stale) subscription configuration, but there is no such option/message.