Every so often the Divi custom CSS file (?et_core_page_resource=et-divi-customizer-global-cached-inline-styles4:1) fails to load on the site. It seems to be at least once daily at times, sometimes more, sometimes less.
I have to go in, recheck the files, clear the caches, and wait until the next time it happens.
The error in the Developer Tools is: Failed to load resource: the server responded with a status of 404 (Not Found).
Do you have any ideas on how this is happening? Does it have to do with the WPMUCDN?