Updates to workflow is not updating attachment to an email as a step within the workflow

I have a workflow that contains several send email steps to send an email based on certain conditions.  The email messages have a PDF attachment.  I have updated the workflow to change the attachments and to change some of the text within the email messages.  I made the changes to the workflow in my development org in the solution that contains the workflow; I exported the solution and imported into a test org.  However, the PDF attachments are still the old attachments; they did not get updated--though the text of the email messages is updated.  I tried a few different options with the workflow within my solution before exporting/importing--left workflow in dev org published, unpublished it in dev org and in test org--but I keep getting the same results where the attachments to the email messages are not updated.

Our current version of CRM on-premise is CRM 2013 SP1 UR3.

Any thoughts on why this happens?