is the flexi task somewhere at beginning of the workflow?

if so, try to place a pause action at the very beginning of the workflow.

Hi Marian, 

I tried adding a pause for one minute at the beginning of the workflow. The result was the first un-formatted email (in the default "response required") appeared immediately. This was then followed one minute later by my previously configured flexi task email.

A bit of history with this particular form. It did have a basic workflow set up previously which was deleted and a new one created. Does Nintex cache these somewhere?

My previous comment got me thinking and tinkering which led to a fix.

My first attempt was to purge workflow data and history from site settings workflow...

This didn't improve things. I then remembered Workflow settings from within the form itself.

Navigation - open the form and from the ribbon click on WorkFlow settings. This will open a page with the current lists workflows. I could see there were two workflows set to allow.

Before removing these I tested which one was producing the correct workflow email.  Once I confirmed that I cleaned up the list to remove the legacy items.

Hope others will find this useful