DNS Problem From USA

Hi,
We have small problem and we need your help.

We are using DNS service from Cloudflare.

When we try to enter our page, sometimes get Cloudflare Error 520 page. But we know that our servers working. When we click refresh page, it works clearly.

This problem for only USA. we tryed from different country and we didnt get error.

When we close Proxied we didnt get errors.

How can we fix this problem ?

Thank you

How can we fix this problem ?

Thank you