Every time I want to watch WCVB (the Boston ABC station), usually the news, the channel randomly cuts to black screen for a few seconds and then goes back. Sometimes it happens every 10 seconds or so, sometimes almost never during a half-hour news broadcast. I'm hooked up with component cables because I don't have an extra HDMI cable. I've tried the trick where you turn off all resolutions in Options other than i1080 or whatever it is. I've also tried turning the box off then on. It doesn't work.
Contact the engineering department at WCVB if you only have a modem and a single cable box with no extra splitters other than a 2 way for the 2 devices. They may have other complaints and a resolution.
With WCVB selected, hold in the select button for 10 seconds and hit the up arrow. What is the IB freq and level and s/n? If the level is between -8 and +10, it's not a level problem. You may have ingress on that frequency. Need to see what it is...
I did what you asked and checked out my inband quality, and got -9.0 dB mV, 36.0 dB. There's something under it that looks important, too: Inband Errors (Corr/Uncorr): 310/275.