I recently discovered that on some of our Comcast channels, my receiver is only outputting in stereo as opposed to Dolby Digital 5.1. Many of the other channels do properly output in 5.1. Additionally, streaming services seem to work fine in DD 5.1. The Comcast channels that are only outputting in stereo consistently do this, so it is nothing intermittent. I checked that the audio track being used is the English - Dolby Digital one. I did a search here and couldn't find anyone else that has experienced this issue. Any ideas?