Same issue as yours..
Bad Gateway
I recently had the same issue "Bad Gateway". I finally contacted Fios support through on line chat and they were able to fix this remotely. It was fixed within a couple of hours after I reported the problem.
I had the same issue. And I'm experiencing frequent picture blackouts. I can hear the TV, just no picture. So far, I've been able to shut everything down and restart FIOs TV to get the picture back. But this is starting to get very annoying.