I’m just starting to watch massive engineering mistakes which was recorded on my v6 box and the first few minutes are all blocky and unwatchable and it has also been the same with other discovery HD recordings. Is there a signal issue to my house.
Is this happening just on recordings, or is live TV affected too? If it's just recordings then you could be looking at a disk problem, but if it's affecting live TV then it's more likely to be a signal fault.
Ultimately the best way to get such faults diagnosed and rectified is to call faults-CS and they can progress it immediately (fault tech visit is likely), or the forum team will probably wade in after a few more days.
Just as an "in the meantime", do you have any problems with Eurosport 1 HD (521), BBC Scotland HD (162 in England), Lifetime HD (208) or History HD (270)? According to DBR, these are carried on the same frequency as Discovery HD so logically would also be affected by a signal issue there.