520 error

From a few weeks on two host many links (pictures or inner links) are broken with error 520. But some are OK (code 200 or 301). My websites use CloudFlare but without is the same. Sample errors:

1. Inner link – broken
https://www.kredytmieszkaniowy9.pl/out/pko-bp-mini-ratka/
Log: === Kod HTTP: 520 ===

Response headers
================
HTTP/1.1 520 Origin Error
Date: Tue, 25 Jul 2017 08:58:40 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: close
Set-Cookie: __cfduid=d8e4a02ed2dc0133e264d9544b89e66781500973120; expires=Wed, 25-Jul-18 08:58:40 GMT; path=/; domain=.kredytmieszkaniowy9.pl; HttpOnly
Expires: Thu, 01 Jan 1970 00:00:01 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
X-Frame-Options: SAMEORIGIN
Server: cloudflare-nginx
CF-RAY: 383deb3128872ac7-WAW

Request headers
================
GET /out/pko-bp-mini-ratka/ HTTP/1.1
Host: http://www.kredytmieszkaniowy9.pl
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
Accept: */*
Referer: https://www.kredytmieszkaniowy9.pl
Connection: close
Range: bytes=0-2048

2. Inner link – ok
https://www.kredytmieszkaniowy9.pl/out/deutsche-bank-tani-kredyt/

Log: === Kod HTTP: 200 ===

Response headers
================
HTTP/1.1 200 OK
Cache-Control: no-cache, no-store, must-revalidate
Content-Type: text/plain
Date: Mon, 24 Jul 2017 03:58:41 GMT
Expires: Sat, 26 Jul 1997 05:00:00 GMT
Pragma: no-cache
Server: nginx/1.11.8
Connection: Close

Request headers
================
HEAD /SH8j HTTP/1.1
Host: tracking.affiliate44.com
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
Accept: */*
Referer: https://www.kredytmieszkaniowy9.pl
Connection: close