Netgear LM1200 dropping connection to Router

My current setup:

Verzion SIM (Account Unlimited no throttled)

LM1200 LTE Modem (Bridge Mode)

Untangle Router (Intel Nuc)

AC1700 (Nighthawk Accesspoint)

Over the last year  i have been having issues where my bridge will sever the connection to my router at random times.  The only way to resolve the issue is to reboot my router.  I have replaced the LM1200 LTE Modem, i have gone through 4 different Routers(3 different untangle boxes) and 1 Nighthawk router.  

Mo router has no error logs to why it would lose connectivity from the bridge, I see other people having similar problems, i have tried setting to factory settings.  I have adjusted the MTU packet size to make sure that the VZW network isnt oversaturated with big packets.

Please help, I am in need of a more stable internet.  hoping there is something that can be done.