How do I delete a Workflow Manager 1.0 child scope with permissions messed up?

How do I delete a Workflow Manager 1.0 child scope with permissions messed
up?

I have Workflow Manager installation with an
"OAuthS2SSecurityConfiguration" applied to the child workflows that I want
to delete.
When I run any of the commands below, I get an "internal server error".
Since I see nothing in the EventLogs or local logs, I can only assume that
this is an authentication issues (I have deleted workflows in the past
with no issue.)
var dcli = new
WorkflowManagementClient("http://host:port/PubSubActivitiesSample")
dcli.Activities.Delete()
dcli.Workflows.Delete()
dcli.CurrentScope.Delete()
I've also tried overwriting the workflow with a null security
configuration. I get an internal HTTP error on that too.
Finally I ran the following powershell command:
remove-wfscope -ScopeURI http://myhost:12291/PubSubActivitiesSample
I get an internal server error for this as well:
Remove-WFScope: An internal error occurred. For more details please see
the server logs. HTTP headers received from the server: ...