Mild Pixelation

I am still seeing mild pixilation on premium channels-- you have to look closely to see that it actually is pixilation-- the picture actually appears to float or move slightly, intermittently, maybe every ten or fifteen minutes. I've attenuated down to the recommended levels and it still happens. I have three tivos-- Roamio pro, Elite and Premiere-- it does it on all of them. I have Comcast coming out to check the lines. Diagnostics don't show any errors. Is anyone else seeing anything like this? This only started happening since the latest update. Coincidence? Any thoughts? thanks