With 11.0, we have provide additional measures to prevent duplicate invoice and diagnostic creation on the app.  From the Today's Call screen, when a technician clicks the Diagnostic or Invoice button for the Service Call, the software will first check to see if there are any open invoices (Invoices that are not in a Status of Complete & Paid).  If so, it will list those Invoice and give the technician the ability to choose to use an existing invoice or to start a new one.  The same logic applies to the Diagnostic.