Pixelation on main box , none on mini

[ConnoA01]

First time post. 
lot of pixelation on sky Q main box (especially sport) which is viewed via a 10 yr old plus Sony Bravia TV.

viewing on mini box via a newish LG tv is fine.

sky engineers have visited to check dish and wireless signals.

Could the TV be the problem? Sony KDL-40W5500