Regardless of network infrastructure or configuration, waiting minutes and having success means the software isn't working. Local request do not make a round trip to the cloud. The android inside simply make a direct call the the url you define as your local request.
So in your local server you should be able to see when a request is received, make a request from Ubi then check your local server, what is lagging behind - Ubi or your server. In my local setup I have Ubi fire a request to my computer, as soon as Ubi light goes off after I talk, I can see the request hit my server, it's instant, my computer use ethernet while Ubi use wifi (2.4GHz).
Someone else reported this but we have not been able to replicate it on our end.
I have several web servers on my computer and they are all basically instant.