Have you tried a new HDMI cable? Have you tried all of the HDMI ports on the TV ? Then, put a different TV or computer monitor onto the V6 and see if that behaves itself - if it does then the V6 is fine its something to do with your TV and V6 interaction. What TV model is it (4K?). Also, what Hub model do you habve and how do you have the V6 connected to the Hub? What does it say in Settings>Network>Connection details about the quality of that connection ?
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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.