BGW210-700 connection issues

I need help my gateway does some kind of reboot or reset a couple of times a day. it's quick when it happens the bottom 2 lights blink red then go back to green takes a 2-3 min if that. The problem is we work from home and when that happens our work vpns have to restart as well as our work phones so we drop calls all the time. ATT tech tell us to reboot that doesn't help they changed the gateway that doesn't help. tech service rudely said they have run test and see nothing try calling when it happens. well it takes longer to get someone on the phone and when I do the issue is gone is it possible on of the two lines bringing service in is going bad and the other one cant handle any advice please