Problem: AR-300M with Verizon MiFi 4G LTE Global USB Modem U620L

I bought AR-300M to use on the road to provide Internet to several devices from Verizon USB Modem U620L. I set it up in “Tethering” tab and It works for limited time but then devices start reporting “Can’t find DNS server”. After I restart the router the connectivity gets resumed and then gets lost again after limited time. When I connect USB modem directly to my computer the connectivity stays up with no issues at all. Any advise would be greatly appreciated. Firmware 2.264

Can you set up custom dns server in Internet connections.

I tried doing that and still see the same behavior.