Is this only happening when you're watching recorded or "paused" programs? Or is it also happening on live TV as well?
If it's affecting live TV channels, it's potentially indicative of a signal fault. If it's affecting only programs which are being played from your hard drive (i.e. recorded or paused), then it's potentially indicative of a hard drive problem.
Either way, it will probably need VM to intervene, by means of you reporting the problem to faults C/S.
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