We're experiencing intermittent 522 errors on various resources with SSL/TLS enabled

Hello, Community,

We've spent several days debugging this issue ourselves with no success. We’re working with a very simple setup:

Nginx configuration with a server-side Cloudflare certificate installed

All relevant keep-alive and performance settings enabled

We have only one location block:

location /test/ {
    rewrite ^/test/.*$ /header.js break;
    root /usr/local/tomcat/webapps/ROOT/javascript;
}

location /test/ {
    rewrite ^/test/.*$ /header.js break;
    root /usr/local/tomcat/webapps/ROOT/javascript;
}

location /test/ {
    rewrite ^/test/.*$ /header.js break;
    root /usr/local/tomcat/webapps/ROOT/javascript;
}

location /test/ {
    rewrite ^/test/.*$ /header.js break;
    root /usr/local/tomcat/webapps/ROOT/javascript;
}

The issue:
During a load test with 50 simultaneous connections, everything works perfectly in DNS-only mode.
However, when switching to Proxied mode with SSL/TLS enabled, we intermittently get 522 errors.

It appears to match the behavior described in this post:

https://community.cloudflare.com/t/random-522-error-or-20-seconds-timeout-but-no-issue-on-direct-ip-access/700318

We've verified:

System file descriptor limits are set to maximum
Disk I/O is not a bottleneck
The server has 32 GB RAM and an 8-core CPU — so resource limits aren’t an issue
CPU load is low
HTTP/2 is enabled
SSL caching is active

Does anyone have ideas on what could be causing this?
Any insights would be highly appreciated.

ivanOP•6/5/25, 8:19 PM

This issue affects our live application — users initially see a blank page, and after about 20 seconds, the page loads with broken styles or incomplete functionality.

kranium•6/20/25, 2:24 AM

@ivan im experience something similar. did you figure out what the issue was?

We're experiencing intermittent 522 errors on various resources with SSL/TLS enabled

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