Issue
Since applying update 20.9, when attempting to log into Siebel application with Browser Scripts in a reverse proxy server environment, the page is blank. A Brower refresh was required to get to the Home Screen.
Solution
The bug is fixed in Siebel 21.4. To work around the issue for versions before Siebel 21.4, there are two options:
1. Disable the browser scripts
OR
2. Turn on HTTP Keepalives on the Proxy web server