Trying to edit pages results in endless loading

Issue Summary

When trying to edit pages on the Legacy Editor, the editor keeps on loading and displays the message "It's taking longer than usual to load this page. This page will automatically reload."

Upon expecting the page's storage format (^...>Advanced Details>View Storage Format) we find the tag <div class="error fatal-render-error">

Steps to Reproduce

1. Find a page with the tag "<div class="error fatal-render-error">" on its storage format or create a page, publish it and update its storge format with the tag "<div class="error fatal-render-error">"
2. Try to edit the page

Expected Results

The editor loads as expected

Actual Results

The editor gets stuck on a loading screen with the message "It's taking longer than usual to load this page. This page will automatically reload."

Workaround

Replace the content of the tag from "<div class="error fatal-render-error">" to "<div class="">"