xml file could not be opened for mode a as a file of charset UTF-8 (2,668) in PO Dispatch

Once or twice a week, we receive an error on the PO Dispatch BI Publisher.  This process runs daily, but only errs occasionally.  It runs on schedule at 5am after the PO_AUTO_SRC.  Most of the time, a restart later that morning, runs to success...without making any changes or correcting anything.  The error states the following:  xml file could not be opened for mode a as a file of charset UTF-8 (2,668) PO_DISPATCH.PO_XMLP_XMLFile.OnExecute Name:populateXMLFile PCPC:6 1391 Statement:836 Called from:PO_DISPATCH.PO_Dispatch.OnExecute Name:writeXMLFile Statement:21 Called from:PO_DISPATCH.PO_Dispatch.OnExecute Name:XMLPdispatch Statement:48 Called from:PO_DISPATCH.PO_Dispatch_Email.OnExecute Name:dispatch Statement:67 Called from:PO_DISPATCH.EMAIL.GBL.default.1900-01.