Zoho Flow / Zoho Books Bug -> Send Estimate

Zoho Flow / Zoho Books Bug -> Send Estimate

We use Zoho Flow to create and email an estimate to our customer. This works quite well. But if we want to send an estimate using a template from Zoho Books which has an attachment, a fixed one, not the estimate itself, this "fixed" attachment is NOT attached in the email.

If we send out the email manually from within Zoho Books everything works fine, and we get two attachments as expected.

Is this a bug in Zoho Flow?