I have installed webreporter 5.2 on a test machine. After installation I want to login on http://172.21.2.10:9111. The login screen shows an error and in the server_err.log I can find the following line:
Make sure you include "/reporter" at the end of your URL when you connect. That is the correct way.
When the browser connects to the server, there is a handshake performed that may not work if you don't use the correct URL. Generally you don't need to clear the cache after upgrading since the client app will auto-upgrade. Downgrading to an older version does require you to clear the java cache.