Well I was thinking about this problem tonight and I thought it could have something to with TP-LINK Wifi Router, so I turned it off. Instantly I had perfect picture with absolutely no jitter or scrambling.
I re-powered the wifi router and in a few seconds the TV picture was back to it's old crappy 3 year old's mosaic picture.
So I investigated more and move the wi-fi router further away unplug all the networking cables, except the power. Same problem, picture became scrambled again within a few seconds. So I move the wifi router even further away from the TV decoder, about 9 meters away. Guess what, same problem.
Could it be possible that the single UHF aerial on my roof is somehow picking up the WiFi signal and affecting the +1 channels???
Also the strange thing is that I have el-cheapo VEON TV in the kitchen and that's not effected by the wifi router at all. Very confusing.
And another thing, I have a pair of 2.4Ghz Panasonic DECT phones, and they too are not affected by the wifi router.
Are DishTV decoders just s**t?