Actually, the Siteground offered a solution for the time being. Please kindly read the section which is related to the issue on this article:
The article is updated and the Siteground section is added.
But please consider that this issue should happen only in the staging environment. If this is happening on the live site too then it might be originated by another cause.
Kindly check the solution they offer and if it is not working for you get back to us with your website information and the name of the page you test the Cornerstone in to follow up. You can add the information privately using the Secure Note functionality of the post