Sorry, can't answer your question. However, I have the same problem and its on just about every station and it happens ALL the time. I just switched to Fios and am regretting it. VZ Tech already been to house and indicated everything checked out ok.
Well, problem persists and know VZ coming back....
Moast common reason for pixelation is loose connection.
If it is happening on all TVs, then try connection at the ONT. Depending on where you are cold weather could have affect connection. Check all connections from there to first splitter for TVs.
If it is only a single TV, check its connections from STB back to splitter.
Could possibly be a splitter issue as well.
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