When you navigating from page to page and hit the 502 Bad Gateway Error, then possibly the first steps you need to troubleshoot was examining the cookie and the page URL that you are hitting the error. The program that I use for troubleshooting was ieHTTPHeaders where all the details of header, cookie and session will be captured in this program.
This is the error title you got in the web page you have during the URL redirection.
The proxy server received an invalid response from an upstream server.
This is the error description after the title and you know that the web server you visiting is a proxy server.
So what is the invalid response from upstream server means?
One possibility happens here is the proxy server tries to redirect your HTTP request to a server sitting behind the DMZ via the ProxyPass configuration.
That happens in my case of error where this error was due to firewall block the connection between the Proxy Server and the server configured in the ProxyPass.
You got to check what is the port and request the firewall team to open it in order to solve the issue.
Next» URL Firewall Configuration url_fw.conf