I've updated my NEXUS 5 to 5.1 and I still have the same problem: can't see my devices over the 3G/4G network. As soon I've move my connection on wifi is working.
As an suggestion: I am accessing my website that is hosted on my pi, and my page has a lot of buttons. It is frustrating because the page is moving up/down based on timeout expiration for address bar and I am pressing wrong button. If the
address bar is invisible and I want to press a button, address bar became visible and I am pressing the button above.