I have just been having a Google around and as it happens there is somebody on the YouView community who has reported a very similar issue to your own: https://community.youview.com/youview/topics/com5-arqa-arqiva-a-issues
So you may need to check that your aerial is at its optimum position and/or that you are tuning to the best transmitter for your location, you can find lots of information about that here: http://www.digitaluk.co.uk/
