Invoice emails not reliably sent when multiple billing profiles share the same recipient address

When multiple billing profiles use the same recipient email address, the invoice sending process does not work reliably.

In our case, we have three billing profiles with the same recipient email address. When invoices are sent, the expected behavior would be that each invoice is delivered correctly.

However, the actual behavior is inconsistent.

Observed behavior:
Sometimes only one invoice email is delivered
Sometimes two are delivered
Sometimes none are delivered

This makes the invoice delivery unreliable when multiple billing profiles share the same email address.