Pixelation and sound problems happen when the signal for the channel you are trying to watch is too weak or has too much noise, most likely due to a poor connection between the cable box and Comcast's network, usually in or near your home.
Troubleshoot by checking all connectors for corrosion and tightness, and by looking for damaged coax cable. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. You might also try unplugging the cable box/DVR/digital adapter power cord for a minute or so.
If you can't find the problem, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. Ask them to check the account setup and send a refresh signal to the box. If they can't fix the problem remotely, insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast cable box/DVR/digital adapter or anything outside your home, you shouldn't be charged.
Bruce's suggestions would be valid if we didn't want to be caught watching Fox channels so we unplug the box and sneak off to the far corners of our homes and plug it back in to a long cable with a poor connector. Of course, then it would happen to all the channels.
Is the Fox signal somehow different than every other cable channel because this ONLY happens, every few minutes, on channels 13, 33 and 48, which are all Fox channels.
This is happening on our DC50X cable boxes.
Most often, the video goes black and the status code 225 error message comes up for about seven seconds:
"The video signal has been interrupted
Status Code 225"
Sometimes the video freezes and the audio repeats one syllable, "gee gee gee gee gee".
I don't remember either problem occuring during a commercial but I could be wrong on that.
Unplugging the box has no effect.
Again, is the Fox signal somehow different than every other cable channel? Why/how would any problem only specifically happen to one network?