I have a problem with 2 HD channels - Channel 5 and F1HD, where every so often the picture pixilates for now reason. I have changed the HMI cable and swapped the TiVo 6 box (I have 2) and checked the signal strength which is 99%. The cable runs from the front of the house around the back on the outside wall and has no contact / cross any power cables and is about 30 meters in length. The pixilation can be recorded and replayed and does not occur on the respective non HD channels nor does it occur on some of the other HD channels I watch which suggests it might be the frequency the 2 channels are being transmitted on.
This is very frustrating especially when you pay the full pack price.