I have same issue. Engineer has been out no fux to the problem as they can't see one? I phoned to cancel the tv package at which point they upgraded me for free TiVo 6 boxes n new hub which they said would hopefully rectify it. It hasn't! Unwatchable. Completely wasting my time and money watching pixelated blocks! They'll be getting a call in the morning!
I had an engineer out as well but like you nothing. It was suppose to be a senior engineer but that did not happen but now having a senior coming in a couple of weeks. It's so frustrating they can't locate the issue
Ok, after three engineers this problem 'seems' fixed. There was a couple of blocking moments during a Channel 4 HD programme Sunday night but that could just be coincidental random glitches and generally everything seems better. The engineer said that the problem was that there was way too much signal coming through to my house. A network engineer had to go to the relay box up the road and did something to slow the signal from there. Normal attenuators screwed onto the back of my Tivo and in my external brown box didn't work - so that was why something had to be done by the network guy to the relay up the road. Anyway - as I say, things seem to be working ok at the moment. Hope that helps some of you guys with the problem too.
Things seemed much better - still the occasional 'blocking and lining' but much less than before. Then Friday night it started up again while watching Channel 4 HD. During 'Gogglebox' the picture degraded to virtually unwatchable - like before.
I've called and an engineer - now the FOURTH - is coming Weds.
Picture break up and blocking started for me a few weeks back and is getting worse, not on all channels though, Good Food HD is currently unwatchable for example, Sky sports HD has also started blocking up as well though not as bad but hadn't noticed it on there before today. I was also getting huge drop outs on the internet connection as well, speed dropping from 200Mbps down to as low as 1Mbps but haven't noticed that the last few days.