UPS return service issue

1. I am receiving the below error message after the implementation return service.

Failure: Invalid merchandise description of package (120623)

Code what we used.

if (isset($return_order) && $return_order==1) {
  $returnService = new \Ups\Entity\ReturnService;
  $returnService->setCode(\Ups\Entity\ReturnService::PRINT_RETURN_LABEL_PRL);
  $shipment->setReturnService($returnService);
}

2. If I also use the below code then it gives as mention error

Failure: Shipment/ReferenceNumber is not allowed for this shipment (120541)

Code what we used.

if (isset($return_order) && $return_order==1) {
  $referenceNumber->setCode(\Ups\Entity\ReferenceNumber::CODE_RETURN_AUTHORIZATION_NUMBER);
  $referenceNumber->setValue($shipping_reference_number);
} else {
  $referenceNumber->setCode(\Ups\Entity\ReferenceNumber::CODE_INVOICE_NUMBER);
  $referenceNumber->setValue($shipping_reference_number);
}
$shipment->setReferenceNumber($referenceNumber);

3. If I also use the below code then it gives as mention error

Failure: Invalid merchandise description of package (120623)

Code what we used.

if (isset($return_order) && $return_order==1) {
    $referenceNumber->setCode(\Ups\Entity\ReferenceNumber::CODE_RETURN_AUTHORIZATION_NUMBER);
    $referenceNumber->setValue($shipping_reference_number);
} else {
    $referenceNumber->setCode(\Ups\Entity\ReferenceNumber::CODE_INVOICE_NUMBER);
    $referenceNumber->setValue($shipping_reference_number);
}
$shipment->getPackages()[0]->setReferenceNumber($referenceNumber);

I'm using the following package, https://github.com/gabrielbull/php-ups-api

I am passing the description on the package below. I just removed "box type" and it works like boom.

$package->setDescription("box type : ".$box_type)