Tuning adaptor issue

I have a Cisco tuning adaptor with tivo and cable card.  For the past month I have experienced pixelating problems on multiple channels.  Cox tech has been out 3 times and I’ve replaced the tuning adaptor.  Today CNN started pixelating again.  I disconnected the tuning adaptor and it cleared up.  I can’t get the switched video channels without adaptor but I can actually watch tv without the digitization.  Any idea?  Is it just a bad adaptor?