I had the same issue .... but after changing to another channel, and back to the channel which froze earlier on, the channel can be viewed per normal ..... after 5 mins, the channel freezes again.
But after swopping to another box, the issue disappear, so, it was a DVR box issue ... suspect some batches of the DVR box had issues, since it's refurbished ... maybe ask them to bring 2 spare ones . ..
Well lets see how it goes after tomorrow