The "Protection" feature of ChangeAuditor (v6.9.3131.1) to prevent changes to certain AD Groups is used. The Active Roles service account isn't allowed to modify these groups (it's still a Domain Admin, but Change Auditor contains a very specific/limited list of accounts which are allowed to modify these "highly sensitive AD groups", and the AR service account is not part of that).
When ARS is used to modify a protected group in ChildDomainName.DomainName.com, Active Roles just hangs. No errors, but it never continues and needs to be forced closed.