Lb1120 AT&T only 3g

When I reset the device before putting in my apn info the router reads 3 bars or 4g (which is the best internet solution for my area) then once I enter in the apn info it goes to 3g. I’ve owned this product for a little over a year and have never ran into this problem. Also at random intervals the device will just loose signal from the antenna (Proxicast 8 dBi High Gain External Magnetic Antenna Compatible with AT&T) wiggling the connectors in the back with bring back the connection, also the connection with just drop without warning with still 3 bars of service showing on the device and on the device website showing a connection. I have the router plugged into a modem most of the time, but it still happens when I plug straight into my PC.

This is my only source of internet because hues net is a joke any help would be appreciated thank you :)