There are two possible reasons that could cause the issue.

Plugin(s) Conflict

Some of the cache plugins could optimize JS files incorrectly. This will lead to an error in JS files which may affect parts of the Visual Builder.

Shortcodes that are part of 3rd party plugins could have incorrect HTML markup which may affect HTML markup of the Visual Builder.

Disable all your plugins and see if the problem persists. If everything is working once the plugins were disabled it means there's a conflict with a plugin or maybe even a set of plugins.
Enable the plugins one by one to identify the one that is creating the conflict.

Broken Layout

Incorrect HTML markup could break the HTML markup of the page layout. WordPress doesn't fix incorrect HTML markup automatically and a broken layout may be causing this error.  

The broken part of the layout can be found with help of the Divi Library feature. You can save the page layout to the Divi Library and load it on another page. Remove each module and section one by one in order to find the broken one.

Restoring the previous revisions of the page could help if the layout was not broken from the beginning.

 

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