Sorry for inconvenience, we are working on Content Managers update. As we are aware content disappearrs only when you try to use Revisions, am I right?
You can’t put content back to cma_layout_data field without “stringifing” it i.e. escaping special characters and adding to special input that holds CM content.
I can repair your page if you create temporary user account for me and if you give me page’s JSON.
Please mark reply as “private” when you share login credentials.