I have replaced the HDMI cable with a quality new one. I have owned the TV for about 6 months and the pioneer for 4 months, no problem until now. It seemed to start after a Sony software update which was automatically downloaded.
The sound drops off from our Sky cable box, but not if we use the TV speakers.
The Sony model is KD 49x8505B
Hope this helps you
No, nor have I reset the factory defaults on the Pioneer. I'm happy to do that if you feel it will help. In what order and is there anything I should be particularly careful with.