STB box not working with subscribed channels

Hi there, so the same day we got Verizon installed (one week ago), all channels we checked worked in the morning., Later that night, a few of those same channels were reading as "unavailable", not "unsubscribed". We changed the coax cable after turning things on and off. The next day they were working. Well, last night, some channels were showing up as broken images, or pixelated.  And they are frozen. Same thing today. Could it be a faulty box? The other little box in the other room is not having problems.