I need to start workflow when DocuSign (Web Import Services) imports new signed documents into repository. I created a workflow starting rule when 'Entry Created.'

However workflow sometimes starts  and sometime does not. To troubleshoot, I placed in starting rule the one condition - 'Path contains', in workflow itself the only activity - Email, that contain started Entry Name. For example DocuSign Envelope has 3 documents: Document, Attachment and Certificate. Sometimes workflow never starts, sometimes it starts when main document is imported, other times it starts twice when attachment and certificate are imported into repository. 

What needs to be done so that workflow starts reliably for any imported by Web Import Services document? Or, once per all documents in Envelope.