Does your 4G ever drop for a few seconds or a couple of minutes?
From my house I usually have 2 or 3 bars of 4G...so sometimes (about once a day) when i'm web browsing on 4G it will just drop (4G logo in the top right corner disappears and its just bars...then the 4G logo comes back but it is white (it only works when it's blue.)
this just happened to me for a few minutes, turned the 4G off and then on again (i use a widget from Go Launcher EX to do this), didn't do anything. but now it's back but did it on its own
same thing with this guy