I have tried and it seems OK. Hard to say more without knowing the "BAD" content.
Generally, the problem might be on server side, perhaps they are doing A-B testing or something.
Another issue is that redirections go bad - many sites are using cookies in redirection process; U++ HttpRequest tries to emulate the browser as much as possible, but of course it does not store cookies persistently, only across redirections.
In any case, I recommend putting HttpRequest::Trace into code to trace all HTTP comms in log, then perhaps you can compare them to Firefox logs (headers and such) or perhaps Chrome logs...