Hi Adwin,
Thank you for reaching out to us. I tested the builder and it seemed like a third party plugin conflict. i disabled the Heartbeat Control plugin and this seems to have fixed the issue, however your homepage still opens in a classic text editor, have you tried to edit this page outside of Cornerstone?
I randomly checked other pages including creating a new page and all seems to be working fine now except your homepage, my guess is somehow that page was edited outside the Cornerstone that’s why it’s no longer editable in Cornerstone.
You can still check for other plugins conflict as you’ve many active third party plugins by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Let us know how it goes!