Ignoring all of the Varnish stuff above, my question is when would the plugin return a "-1" as the result? Also why would it do it on all of the 4 functions at the same time? If I can figure that out then I can make Varnish work around it. Ideally it would be best if it never got that response though :)
I should add that I've never once seen this response when bypassing the cache.