Channel Failed / CS2004 Errors across both TV 360 Boxes

Hi,

For the past couple of months I've been having frequent, intermittent channel failed / CS2004 errors popping up on both of my 360 TV boxes. These pop up every couple of minutes very briefly then disappear, and they're accompanied by a lot of pixelation on the picture as well in between. It seems to happen on all channels, it isn't isolated to a particular channel.

I've followed all the online guides related to this error code, checking for loose cabling etc., but that hasn't fixed it.

The feed to both 360 boxes comes into my house through two separate cables, so I'm suspecting there is an issue in cabling or signal which is common to both boxes, and might originate in the brown Omnibox outside my house perhaps?

I previously contacted live chat who tried to fix it remotely via a software update, but that didn't resolve the issue.

Can somebody please help?