I've seen this happen on any rom whether it be stock or custom. WiFi tether or stock tether. I can't vouch for USB tether as I don't use it much. Basically the 4G stops working all together. My Hotspot will still be on. So what I do to fix it is go in my apn settings and refresh the connection by selecting an alternate or selecting an alternate and setting back on the same apn. Does anyone have an answer for why this happening? Is it the note 3? Or is it t-mobile? I've ran a speed test when this happens and it does not send or receive packets.

Bear in mind I am not extremely tech savy. I just got an S5 when the S6 came out, AT&T, and I don't know if it is just my phone, if I've done something wrong. What I'm trying to figure out is, why when I am in Facebook it will freeze and occasionally close?