The 500 code errors that I see state “Unhandled AJAX error. Expecting valid JSON from response”:
Unhandled AJAX error. Expecting valid JSON from response. Object { readyState: 4, getResponseHeader: getResponseHeader(), getAllResponseHeaders: getAllResponseHeaders(), setRequestHeader: setRequestHeader(), overrideMimeType: overrideMimeType(), statusCode: statusCode(), abort: abort(), state: state(), always: always(), then: then(), 11 more… }
I don’t see any 406 so I’m now doubting you are referring to mod_security whitelisting. So since the URLs you referenced are all local to the site itself, I verified all permissions on those directories are all “0755”.
Please let me know what to do next - perhaps you can be specific as to what white listing you are referencing.
Lastly, I’m also receiving occasional messages when attempting to edit a content page with X Pro that state “A conflict on the front end of your site has prevented the preview from loading.” It seems I’m able to bypass the message, but all the above problems still exist too. I’ve also tried increasing PHP limit to 2048MB on server.