The "access-mechanism" field in core-service=management/service=active-operations/active-operation=* is always undefined. The code that sets it is using the wrong var:

ModelNode accessMechanismNode = model.get(ACCESS_MECHANISM);
if (accessMechanism != null) {
    accessMechanismNode.set(accessMechanismNode.toString());
}

It should be accessMechanism.toString()