How to Fix Cloudflare 521 Error with Wildcard Subdomains - Troubleshooting Nginx 502 in Docker Multi-Container Environments-Resolving Cloudflare 521 Errors with Server Log Analysis
Likely symptom
Likely cause
Safe rollback
Verification route
- Repeat the original action, not only a simplified test case.
- Restart the app or reload the service after configuration changes.