The deliver command internally runs subjobs to create a document file to deliver. The name of this file is based on the document ID value of the deliver command, in order to appear as a logical name for an email attachment. If mulitple deliver commands use the same doc ID value and target the same document type (i.e. pdf), the same document file will be used, meaning the first one generated gets re-used on subsequent deliver commands. This can result in an incorrect document if different argument options are needed, such as an args option to specify which copy to deliver of a multi-copy document.
If you need unique documents attached to multiple deliver commands, specify unique doc ID values.