My sound cuts out too. I've contacted VM about this a few times. Keep being told to tweak settings. I do and it fixes it for a few hours. Then have have to go through the hassle of contacting them again. To be honest I've given up watching the V6 box and am just using the services on my smart TV. If someone from Virgin reads this and knows what to do please do get in touch. It's really frustrating. I'm paying a lot for nothing.
Do you have a different tv or computer monitor that you can put on the V6 to see if the problem disappears - which would then suggest its an issue between tv & V6. When I had my "sound cut out" problem on my new Samsung TV (not a 4K) a year or so ago, my first thought was to VM to get the V6 fixed. Which didn't fix anything - so I went onto the Samsung forums (UK & US) where there are literally dozens of posts from people experiencing all sorts of sound and picture issues with their new TV's connecting to their favourite cable TV "box". Long story short... I contacted Samsung UK support who said “one of our representatives can remotely access your TV to perform the HDMI EDID rewriting before establishing the connection with the V6 box and the other HDMI-supported external devices”. Problem solved. In the absence of any VM "fix" for this particular issue I would be straight on to my TV manafacturer's support line to see what they say.
-------------------- Services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.
It was happening due to the V6 box being connected to an Onkyo home cinema amp. It wasn't an issue when directly connected to the TV. I've tried every settings configuration I can find on the TV, the amp and the V6 box. I've also been visited by a Virgin engineer who also just did some settings tweaking.
Virgin's attitude to this is that they do not support this type of issue and that if the box works when attached to a TV it fulfils their obligations.
So... As I enjoy television sound via my home cinema I guess I'm incompatible with Virgin's services so I've cancelled the television part of my contract with them. Which, I guess, solves the issue.