Nighthawk LTE Mobile Hotspot Router – Gigabit WiFi on the Go – AT&T Networks

I purchased the Nighthawk LTE Mobile Hotspot Router, MR1100, from AT&T. The first unit started powering down ramdomly after using it a few days. I have it set to not go to sleep. To get it to turn back on, I need to pop the battery out, put it back together and then press the power button to restart. I exchanged the unit on the 14th day for a new one. It started out fine and after a bout a week, It is again powering down unexpectedly and I need to remove/ reinsert the battery to get it to reboot. The frequency of power offs is increasing. Any ideas? I checked for updates and it is on the current software version available.