Satellite unit drops connection - picks up after refresh (sometimes) - then drops off again. Light does not change from white. The main connection to it is a wireless cable box which recently began...

I am using a Deco P9 behind an ATT Gateway Arris NVG599. I used the instrtuctions from ATT Forum with the information from IP Passthrough under Motorola NVG 510 and 589. I used the DHCPS-fixed option...