Mailgun emails are being sent with empty contents

Hello,

I have been using the Mailgun API to send emails from my website. This has been working fine up until the 3rd of March. There were no updates made to the application which could have caused this, it just stopped working out of nowhere. The emails get sent successfully with a subject but without the html or plaint text contents. There are no errors in the api response, or in the error reporting tool the website uses. Everything works fine if running the server locally, the issue is only in production. I cannot figure out what the issue is, any idea why this could be?