Personally I would always go for the SCART plugs first, I've found they have a tendency to partially disconnect at the slightest opportunity
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Give them all a firm push.
Give them all a firm push.
Ah the yea olde "Turn it off and on again" IT solutionThe sound loss is quite a common issue which can often be fixed by switching everything off and, when the stb is back up and running, switch TiVo on too.