I just had my V6 box installed. Every day when we first turn on the box the screen keeps flashing white and the sound keeps crackling for about 5 minutes. It settles down but the occasional white flash and sound interruption can happen every 10 minutes or so.
I have tested other HDMI sources such as the dvd player which work fine, but the white flashes start as soon as I switch to virgin media.
I contacted tech support on the phone who suggested switching the hdmi sources around which I have done. Have unplugged and replugged everything and turned off and on again. This is a recurring problem.
Tech support said to contact you if switching hdmi sources didn't work to get an engineer to have a look.
I changed the video options on the v6 box so that the options "with pass through" were also ticked. This seems relevant as i have one of those Samsung "one connect" boxes that the hdmi cable plugs into before then going into the tv.
Since I changed the setting not a single flicker.
Hope this helps someone else. Also note that your tech guys didn't suggest this on the phone.