Hello there, I am using pro (latest version) with cornerstone. The website is a multi language ones translate with WPML.
When I load cornerstone on the default german version it works but when I switch to english in the editor while in cornerstone for german the following error message appears:
“The preview could not load due to the iframe response being incomplete.This is most often related to a plugin conflict, or customizations introducing a PHP error.”
Then we decided to clear the cache and then deactive WP Fastest Cache, then the following error message appeared:

We’ve checked all plugins and updated them, so would like to have your assistance here. Thank you!