I have a newly installed DCT6200/2005. The HD Shaw channels 201 and higher have a lot of Pixelation and sound drops. I can live with the sound drops but sometimes the Pixelation is so bad the channels are unwatchable.
Shaw technicians checked all the connections and replaced several boxes in the underground cable joint boxes. Also connected a cable directly from the same joint box to the DCT but the problem remains.
Pixelation is typically a signal strength problem (too much, too little) or a bad box. Your techs should have been able to figure that out. You may want to try unplugging your box and then have Shaw re-initialize it. Welcome to DHC by the way. I'm sure other member will offer their help if I'm incorrect!