Have you called faults to check your signal levels?
Only other thing you can do yourself is check the connections are all tight.
Thank you for reaching out to us here on the Community.
I am very sorry to hear you are experiencing issues with channels pixelating, we will do all we can to help.
Can you please let us know if you are still having pixilation and if yes, is it still only on BT Sports HD or all channels?
Can you also please check that all cables leading to and from the equipment are secure and without damage?