MR5200 - Keeps Losing Connection

We used to have a 3g device with AT&T. That worked great for about 8 years. There is an AT&T tower about a mile from our house (live in a very rural area where there are no fiber optics) and cell service with AT&T is phenomenal. They are transitioning off of 3g and onto 2.4 and 5g so we had to get a new device. They just got a nighthawk MR5200 and it drops consistently. It works great when it's working, but will drop several times a day. Once I restart it, it works fine until it drops again. I have the nighthawk connected to his computer via ethernet cable and have turned the wireless capabilities off. It still drops. Please help, thanks.