The standard advice with all pixellation queries applies here, with some subtle changes for your situation....
Pixellated pictures on live TV are often the sign of a signal fault. If you've rebooted your box once, then there's likely a fault somewhere, so this will need VM to intervene. You're likely to need either an engineer visit or a replacement box, depending on what VM's remote diagnostics turn up.
First check the automated faults line for any existing issues in your area that could be the cause: 0800 5610061. If nothing's reported, assume VM don't know about your fault and ideally you'll need to call them.
In your case, the TiVo doesn't have WiFi so that shouldn't have anything to do with it. But if only one box is affected, then you've likely ruled out an external fault.
Please try swapping your TiVo & V6 boxes between rooms, and see if the problem follows the box or remains with the internal cabling.
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