How to understand DeliverDocument WS deliveryStatus of 'ERROR' in EngageOne Server

Product Feature: Web Service (API)
There are various status responses encountered for an unsuccessful run of DeliverDocument WS.

The statuses are listed below:

'ERROR' status code is returned when the delivery channel fails, because of an attachment conversion issue. (For example, a document attached to a publication is broken and conversion services fail to process it.

This status ERROR is different from a normal document composition failure, which happens occurs when the "main" document generation fails.
UPDATED:  October 16, 2017