APM profile with OCSP Authoring and Clientless mode configured, but need to reload page

You could try to add some logging in your iRule just to verify where things are going and what the URI is. Then from the CLI (using PuTTY or some other SSH client and command

tail -f /var/log/ltm

when HTTP_REQUEST {
    log local0. "URI: [HTTP::uri]"

    if { [HTTP::uri] starts_with "/xxx/" } {
        log local0. "  Routing to IP_address_VS2"
        node IP_address_VS2 80
    } else {
        log local0. "  Routing to IP_address_VS3"
        node IP_address_VS3 80
    }
}

you could also loop and log the cookies that exists for the request if those matter on the back end.

log local0. "  Cookies:"
foreach cookie [HTTP::cookie names] {
     Log the cookie name and value
    log local0. "  $cookie: '[HTTP::cookie value $cookie]'"
}