I have this same problem. The Shaw Internet modem is causing interference with my cable box. If I disconnect the cable modem for the internet every thing works just fine. Several years ago ( 5-7 + years) a Shaw Tech installed a signal amplifier so I know the signal is strong. The modem model is CGM4141SHW (from the attached tag) or CGM4140COM (from the internal firmware). The modem is set up in bridge mode.
The odd thing is that it will work well for a time. Then the pixelation comes back. I have noticed that when one or two devices are removed from the network, it clears up. This is very odd since the cable TV box is not connected to the internet per se. I don't see how they should interfere with each other especially since the cable mode is in bridge mode and connect to a router which should further isolate the cable modem and cable box from each other.
Exact same problem! When modem power was pulled pixelation stopped! The same if i unplugged the coax cable from modem when powered. pixelation stopped too . Utimate Fix was to plug modem into different " wall outlet". All is Good Again.
Found this posting after searching for the same problem. I had been experiencing a lot of pixelization, random lines and blocks, audio cut outs, missing captions every few minutes.
As soon as I powered off the wifi router, pixelization stopped. When I plugged the wifi router back in, it returned. Everything was plugged into one power bar, so I moved the power cord for the wifi router to a different outlet on the wall instead of the power bar. While I was moving it I found a loose plug in the power bar, so the ends were partially exposed enough to unpower my PC when I knocked it. Double checked and made sure all power connections were firmly in the power bar.
Have not had a problem with pixelization for the last few days since I've firmly seated the power connections and used a different outlet for the wifi router.
So as the troubleshooting guide says, unplug and plug in again, both ends of the power cords. Maybe plug your wifi router into a different outlet. Check for any loose plugs.
A good test is to power off your wifi router to see if it stops the pixelization.