Error page showing Apache server details details instead of standard 404 page

unknown

Hi Experts- When you hit a wrong url in the JIRA application, its leading to error .

Eg: https://jxjira.myhost.com/si leads to below page and rest all wrong searches(invalid url searches) lead to proper 404 pages (second screenshot) which is expected. I'm wondering why its only happening when appended with '/si' after hostname. 

Requirement:

I need to either know where can I make a change to display some custom error page without Apache server details. Or a page like standard dead link page would be fine. Please advise.

Nic Brough -Adaptavist-

That suggests that Jira simply is not running under /si and the proxy is getting nothing back from it.

What are your reverse proxy settings?

Where is Jira actually running on the server? 

Do you have a "context" set in Jira's server.xml connector setup?