Error 522 on specific CDN


I came across strange behaviour while trying to understand why my WordPress admin is so slow. It came to my attention that one of the js file was not accessible and Cloudflare was returning Error 522.
So first thing I did is to make sure that file actually exists and cleared all cache and by providing full url to specific file http and https.
The result was the same, error 522.
So I tried different browser, Opera, Firefox, Explorer all off them received same response.
Next thing I did was trying to access this file from other region via VPN, and surprisingly resource is available.

So it seems like resource /wp-includes/js/dist/vendor/wp-polyfill.min.js?ver=7.0.0 was permanently cached on one of the CDNs in KIEV to be precise. All other CDN show resource correctly. If I change the query string let’s say to 7.0.1 everything works.

Did any one came across that issue and knows how to fix it?

That error would indicate that Cloudflare cant reach your server. What is the URL?

Thanks for prompt feedback, the URL is and it’s only failing for request served via CDN located in KIEV

Domain seems to be properly set up and the file is served without issue.

If you say the connection only fails when routed via KBP I am afraid there wont be much the community can do. It would be best to open a support ticket and forward the connection ID of the failed request so they can investigate as to what the issue is.

I’d check if you possibly have any firewall rules in place on your server which could make that connection fail.

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