Can't setup internal location block nor use them in custom locations

[parasiteoflife]

I'm setting up an internal location block for a proxy host using the "Advanced" tab, but any time this is done the dashboard shows the proxy host as "Offline" and no conf file is created.

location @handle_response {
    set $content_type $upstream_http_content_type;
    if ($content_type ~* "application/xml|application/json") {
        return 200;
    }
    return 404; 
}

Same happens if inside a custom location we enter

proxy_intercept_errors on;
error_page 200 = @handle_response;

[Zoey2936]

docker logs?