No, you cannot retune cable boxes. Everything is automated. If the picture is breaking up then you have signal or noise issues affecting the frequencies these channels are carried on. Check the service status pages via the link above. If this shows no issues the problem is likely to be local to your installation & you need to ring faults for assistance.
VM BB TV Landline. Vonage 2nd line. Freeview/Freesat HD, ASDA/Tesco PAYG Mobile. Customer since 1993
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The V helpful Tec came and sorted this out. It turns out that it was an issue of the balance of my signal strength from the cabinet in our road to the house. when first installed that had been set in a goldilocks way, not too much or too little. But more people had been added into the cabinet and we might have been moved on the board and the balance lost. Soon as he fiddled with it and took off our signal reducers we got the balance and channels back.