Suddenly HD signal is intermittent

[Jeremyduplessis]

My Sky HD box has worked for many years. But two days ago I noticed that the signal gets lost for a few seconds but only on HD channels like channel 4. All non HD channels are fine. Nothing has changed. 

[Mark39]

Could be that the dish has moved slightly, particularly if you've had bad weather recently. Or if the LNB (on the arm of the dish) is more,than 5 or so years old, it may be failing. Unless you have Sky Protect, you would need to get a local satellite installer to come and take a look. Or upgrade to Sky Q.