Re: Anyone knows why I have this?

I had the same issue, ended up with multiple NFFromData in my Nintex form on O365.

The only way I could get rid of the issue was to create a new list, export the form from the "broken" list and import it in the new list, along with all the workflows I built.

The duplicated NFFormData are now gone in the new list.

My list is using a custom content type, and as I was building the form and the workflows to meet my requirements I have added and removed fields to both the list and the content type along the way so it might have somethting to do with it ...