That issue is usually due to HTML and CSS syntax errors. If you're using custom HTML and/or CSS in that page, please ensure there are no syntax errors because our builder's preview has a mechanism to temporarily fix errors so that the preview won't break.
One way to find where the error is located is to first remove any custom CSS in the Content CSS. If the issue's not resolved, the cause could be broken HTML. If this is the case, save your page as a template using the Template Manager.
Next, create a test page and load the saved template and remove all the sections except the section with issue. If it's fixed, the broken HTML might be in one of the sections that were deleted.
It's also possible that this is caused by incorrect optimization. If you're using an optimization plugin like Autoptimize and W3 Total Cache, please clear their caches and disable them to check if they're causing the issue. If not, just keep them disabled while the issue persists so they won't stand in the way of our investigation.
If the issue still persists after doing the test, please provide the URL of your test page and give us your site's WordPress Login URL, Username and Password in a Secure Note.