Hi Hoskinshozzy,
Welcome to the Community and thanks for posting.
I am sorry to hear you are having problems when viewing HD channels. It's hard to say what is causing the problem at this point but I am sure we can help.
Can you please confirm the following for me?
Are all connection to the box secure, finger tight with no damage?
Is your box connected to the broadband service via ethernet or WiFi?
Does this problem occur at certain times of the day and on specific HD channels?
Let me know and I will be happy to help.
Thank you
Nat