Multi Registration Confirmation Emails sent when user registered through API

Which App Type (OAuth / Chatbot / JWT / Webhook)?
OAuth

Which Endpoint/s?
/webinars//registrants to add a registrant

Description
We’re utilizing Blackthorn Events within our Salesforce environment for handling of registrations for online Webinars/Meetings. After a user completes the registration they are often receiving 2 (and sometimes even 3) Registration Confirmation emails.

Looking at the registrant list we can see that they have only been added once to the Webinar/Meeting. Using the Zoom registration link does not reproduce the problem. It is only when the registration has been completed through the API.

This is the exact same issue as covered in Two emails sent on registration which doesn’t provide any resolution.