SharePoint WorkflowManager error: Cannot create scope

When trying to create the scope you might sometimes notice following error.

Scope '/myscope/’is not in an active state. Its current state is 'Unregistering'. HTTP headers received from the server - ActivityId: ..

This can happen if you have previously deleted the child scope ‘myscope’. Under some conditions unregistering of scope can take very long time, here long sometimes can be forever.

Following calls will cause this error:

client.CurrentScope.PublishChildScope(../myscope/..);

or

client.Activities.Publish(..activity/..);

or

client.Instances.Terminate(inst.WorkflowName, inst.InstanceName, "Admin");

To workaround this problem, one SQL Management studio and connect to the machine which hosts the Workflow Manager database.
Then carefully execute following statement:

update [WFResourceManagementDB].[dbo].[Scopes] set [Status] = 'Active' where [Status] = 'Unregistering'

NOTICE: The statement shown above is not supported by Microsoft and can possibly damage your system!!!

I did that several time and it worked all fine. Anyhow if you decide to fix it this way it is on your own responsibility.