Unable to send emails through an add-in due to Content Security Policy (CSP)

Hello, I manage an Office Add-in that helps aids in user productivity when writing emails. Part of the functionality of this plugin also includes adding content to the body of the emails. However, the source of the content is external which seems to trigger the content security policy set by Microsoft and prevents the email from being sent. Here is what the error I get when looking at DevTools console:

However, the same add-in works as expected in the Outlook for Mac client. Additionally, despite the content (such as images) being blocked, it is still being rendered in the compose window normally.

I've also noticed this intermittent error when it comes to CSP which I'm unsure if it is related or not:

Has anyone run into this and if so, any tips on how to resolve it? Thanks in advance.