I've been running an automation workflow with Mailchimp for a while, which has a simple welcome Newsletter. The Automation email editor only lets me edit the HTML version of the email, and auto-generates a text-based version.
However, it only generates the plain text version when the email is first created. I have edited the HTML version several times since then, and only just realised that the plain text version is still stuck at its initial state. I can't find any way to edit that plain text version, or even to disable it!