Did you ever get a solution to your problem? The pixelation on my Discovery recording last night was so bad I almost couldn't watch it. I find it really hard to believe that having a bad connection would cause only ONE channel to pixelate.
Actually for us it is all channels on all 9 boxes and we've chatted 3 times been put on hold 2 times and told to go to the xfinity store twice. It's still not fixed and as usual even x comcast employees seem to think it is something we have to fix ourselves. Covid or not as always you comcast guys' lack of service and concern is apalling.