If you've rebooted your box once to eliminate a software gremlin, and have checked your connections are all finger tight, then pixellated & breaking-up pictures is nearly always symptomatic of signal issues caused either by a box or cabling fault. Either way, it will need VM to intervene and remedy whatever underlying fault is causing it.
If you can identify specific channels (including HD or SD?) that are afffected, it can certainly help narrow down the cause in the meantime..
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