Welcome to the forums I'll be happy to help find out what's happening with the recordings playback being pixellated.
I have connected to your TiVo® box (500Gb one) and all signal and power levels look great from here. I can see an high amount of time-outs on the line. time-outs can be normal, in this case this is excessive. A simple reboot will clear this for you. If you can please power off/on your box please and let me know when this has been done and I will re-check the box.
This will in turn help resolve this fault.
In addition to rebooting your box, it's worth checking to make sure all leads connecting the box to your TV are secure and that the box is well ventilated and nothing covering the vents around the box.
Keep me posted on your progress. I'm here to help if you need me
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