After some more investigation, the problem appears to be that when the page is generated, the script tag is being rendered as an a tag and shown as a hyperlink.
So, while we’ve entered the below:
<script src="https://embed.lpcontent.net/leadboxes/current/embed.js" async defer></script>?
When we look at the page source, below is what it displays:
https://embed.lpcontent.net/leadboxes/current/embed.js