I have noticed this for the past couple of months too. I thought it could be temporary, but FB and my Dolphin browser on the TB have been crap. I have noticed that my data will show 4G with full bars and the moment I unlock my phone and attempt to go into either browser or FB, it acts like it knows I need to go into them and drops all data. Get the usual Tap to resend message. Sometimes it will stay connected long enough to load a small news feed page, but then quickly drop when I attempt to view anything on it (pics, links, etc.). I have also seen it do this with the Draw Some game. I'll get a searching for internet connectivity message until it finds the signal again. I find FB almost unusable for the most part. The browser makes no difference either. It stays connected slightly longer, but still very annoying. One thing to note is that its hard to figure out if its really a FB or OS or HW issue as I have seen it drop signal even when stationary and just looking at a locked screen. Without actually using it. I live in Orlando and for the most part it has been smooth with the exception of a few hiccups earlier on when LTE was first rolled out. I'm thinking its something with the radio and/or OS.
I am using my stock TB. Its never been rooted. Using Android 2.3.4 | Sense 2.1 | sw# 2.11.605.19 710RD | PRI version 1.41_002, 1.64_002
ERI v.5