Thanks for posting in!
Please be advised that you are not supposed to switched between editors. If the page were originally built in Cornerstone, when you edit it, you should see something like this in the new editor:
In your screenshot, it shows that you have switched to the WordPress editor and that is why it is displaying the Cornerstone formatting shortcodes. It may corrupt Cornerstone data which may no longer allow you to edit back in Cornerstone.
If the page were built in Cornerstone, please edit it like changing the images in Cornerstone. Do not switched between editor and manually change the images.
Hope this helps.