Click + for User Story and Select a user story. An error is presented: "PARENT CONFLICT This Defect already has a parent"
Environment
Release: Component: ACSAAS
Resolution
If you proceed it will disassociate the current parent work item and associate the work item you select as the parent Item. This is because the defect can have either a Test Case or User Story as a parent but not both. This is working as designed.