external domainname replace and uri masking

Try this instead - it will change all redirects to be this host

when HTTP_RESPONSE {
    if { [HTTP::header exists Location] } {
        set path [URI::path [HTTP::header Location]]
        set query [URI::query [HTTP::header Location]]
        set location "https://my.host$path?$query"
        HTTP::header replace Location $location
        log local0. "Rewriting Location [HTTP::header Location] to $location"
    }
}

Install and run this and check the logs in /var/log/ltm