That looks like some sort of a shortcode attribute or base64 encoded content of some sort. You can try changing this option, but it may not help if that is part of the content.
The shortcodes are probably not registered at that time of execution yet. If that option does not resolve that, then the only option is to change the content field to something else: https://i.imgur.com/H3qMeyS.png
If you have the custom ajax handler enabled by any chance, make sure to turn that off, that may help with the unregistered shortcodes.