Hmmm I do know what you mean, I have the same issue. I have setup formbuilder to email invoice, however when you click the submit on the form it takes you directly to the bottom of the page, however it is totally blank.
When you scroll up you see the invoice/totals of what you selected on the form, also more distrubing is, the label for every field has been displayed at the beginning of every item. Also no invoice seem to be sent to the person to whom has filled in the form. At the bottom of the totals you also get the an icon/button which is of an envelope, clicking on this then takes you to the Thank you page.
Due to the site being used constantly I really can only do the updates very late in the evening, with it not working I have to restore the original form, but I have included some screen shots to show what I mean.