When ProxyErrorOverride is enabled there is a delay in the display of customer error pages in httpd 2.4

Issue

• When I use ProxyErrorOverride and ErrorDocument, the custom error pages take a long time to display. It takes as long as the time specified in ProxyTimeout.
• We have set "Custom Error Pages" for almost all Virtual Hosts in our webfarm. However apache httpd takes about 15 seconds before it shows those Custom Error Pages.