Phenix 1.6.X Cannot Print a Deliver Note

[Bitfarmer]

I wonder if anyone else has suffered from this bug. Everything else works normally but if you try to print a delivery note for an order, you get a Prestashop Exception always

 #1 ($order_invoice) must be of type OrderInvoice,
 	Order given, called in /var/www/sites/phenix/classes/pdf/PDF.php on line 161 and
 	defined in /var/www/sites/phenix/classes/pdf/HTMLTemplateDeliverySlip.php:43

Stack trace:
 #0 /var/www/sites/phenix/classes/pdf/PDF.php(161): HTMLTemplateDeliverySlipCore->__construct()
 #1 /var/www/sites/phenix/classes/pdf/PDF.php(86): PDFCore->getTemplateObject()
 #2 /var/www/sites/phenix/controllers/admin/AdminPdfController.php(493): PDFCore->render()
 #3 /var/www/sites/phenix/controllers/admin/AdminPdfController.php(451): AdminPdfControllerCore->generatePDF()
 #4 /var/www/sites/phenix/controllers/admin/AdminPdfController.php(109): AdminPdfControllerCore->generateDeliverySlipPDFByIdOrder()
 #5 /var/www/sites/phenix/classes/controller/AdminController.php(1160): AdminPdfControllerCore->processGenerateDeliverySlipPDF()
 #6 /var/www/sites/phenix/controllers/admin/AdminPdfController.php(41): AdminControllerCore->postProcess()
 #7 /var/www/sites/phenix/classes/controller/Controller.php(338): AdminPdfControllerCore->postProcess()
 #8 /var/www/sites/phenix/classes/Dispatcher.php(427): ControllerCore->run()
 #9 /var/www/sites/phenix/storeadmin/index.php(81): DispatcherCore->dispatch()
 #10 {main} thrown in /var/www/sites/phenix/classes/pdf/HTMLTemplateDeliverySlip.php on line 43

I have tried for hours to track this to no avail. Any pointers or help would be greatly appreciated. It is a Type error but if so, how did it ever work! I have been thinking that it must be some change in the database possibly from the data originally coming from OSCommerce, Prestashop, and finally to Phenix Suite, but I can't any changes that alter field definitions in the tables.