New replacement Youview box faulty.
1. TV channels breaking and unwatchable, OK straight from aerial to tv.
2. Keeps switching tv on after switching off.
3. Goes through full setup every time it is switched on.
All connections same as previous box, now cannot use it.
Try disconnecting the aerial lead and doing a retune. It will show no channels found but, will clear the memory. Then retune with aerial plugged in.
Have you tried swapping out to different aerial leads as they have been known to fail or to pick up interference .