Dennis @ PerfectForms
You can build “back door” access for yourself. Create a hidden button that when pressed uses a Set Stage behavior object to set the instance back to the stage where you need it, then use a Set Property to make the email address editable, and then use a submit object. Create a behavior on when form opens use a Simple Branch to determine if you are the user opening the instance. If True, make the state of the hidden button normal.
The button should Set Stage and Submit. The instance will not advance to the next stage because the Set Stage will supersede the condition in the workflow join path. An instance cannot change stages unless it is submitted. After the instance is brought back to the stage where you need it, you still need to submit it to change stages and send the notifications that did not get properly sent in the first place.
Save and publish your changes. Map the old instances to the new version:http://www.perfectforms.com/Documentation/manual/html/?fl_mapping_form_instances_to_anot.htm
Open the instance. Change the email and click the hidden button. Then open the instance one more time to submit it again. The notification should be sent to the correct address.