Yes i added a question "commune" feed by pull function.
the question was a copy / paste from another form.
Today, i have just resolved the problem by deleting a view that joined the form's feature service with my workforce's assignments feature service.
Thank you for your answers.
Delaere Mickael was the view you deleted the only view associated with your form? I'm receiving the same error while publishing, and suspect the associated views are the issue. Unfortunately, we have created multiple views and maps associated with our form, and so removing all views would be a large burden just to add a couple of fields.