Watching two recorded simultaneously causes "No Signal" - DirecTV

When we're watching 2 different recorded shows the screen will go black and display the dreaded "No Signal" error.
It also does the pixelated picture, during playback.
If we stop watching one, the other goes back to just fine.
Start watching both programs again, back to the distorted picture and the No Signal error.
[DVR is an HR34-700]

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