Dennis @ PerfectForms
It sounds wildly entertaining, but perhaps one notification would suffice. I would first look at the group to see if users are in the group more than once. Check to see if the individuals are part of the group. Check to see if there are notification behaviors located outside of the workflow (where we recommend that they reside). Perhaps there is a notification behavior on when form submits data or when button is pressed. If none of these yield any results, you can export the form and attach a copy of the .pf file to a support inquiry at: http://www.perfectforms.com/support_contact.php. I will review the form for you.