Just guessing here, it could help if you tell us which proxy(Apache,
Nginx, ...) and app servers you use and how you connected
them(relevant lines of config)
Do you have a firewall between the proxy and the server?
One thing that bit me before are timeouts/lost connections. e.g. the
ajp connector has an infinite timeout, while e.g. Apache has a default
timeout of 60 seconds (I think)
You should configure the same timeout in the proxy and in the tomcat connector.
You can check the connection status on your server using netstat, if
there are lots of open connections ...
