Just swap the two V6 boxes around temporarily to determine if the problem is indeed the box or whether it is with the TV that currently "blacks out". Not uncommon for some TV's (especially new 4K ones) to have some incompatibility issues.
-------------------- 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.
I would like to look in to this further and run some diagnostics checks.
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