I've a list with multiple views.
If I group the default view of my list (it appears by any column) and then republish my Nintex form I receive the following error:
If I go back to the list, the item has saved/updated etc. regardless of the error.
I've created a view, with just the SharePoint ID column viewable (made it the default view), then grouped by another field (randomly selected) and it comes up with the above error. If I don't use the list group by function I can publish the form OK.
I've looked at my controls on the form, all appears as I expect. I've got no rules with 'dead' columns.