Invoices emailed to wrong customer when posting sales invoice

Our main question is how did sales order 8300S103448R001 with invoice 8300100095 get emailed to wrong customer .

We believe when a customer does not have an Invoice email communication method and the user selects to print and email the invoice (via additional documents) since the email value does not exist, here the system is picking the other available address,

Here the customer does not contain communication method for the “commercial Invoice” even when I select the Email check box of “commercial Invoice” on Inquiries>“additional documents” form , the invoice emailed to wrong customer automatically,

while debugging the code I observed that empty email address is coming through code , How can I find that wrong customer mail

Is there any chance through default email set up parameters .

Please help me