Duplicate name when sending invoice

I have two clients with the same name and when I send a invoice, it sends it to both. Is there a workaround to send it by an unique field like the id or the email?

I just added 2 customers, with the same name + email.
I created an invoice on customer 1 and then clicked ‘Sent email’ and only received one email.

Can you maybe describe how to reproduce this bug step by step?

Also, which version of InvoicePlane do you use?