Strange Issue With Local PBS Station (Video Doesn't Move)

Just within the past week, at least some shows on Channel 9 in Seattle quit playing properly on my Fire Cube 3rd Generation. It's an ATSC 1.0 channel still, and what happens is the video will display the first frame, but not play further, despite the audio playing. If I switch playback to hybrid it will play properly, but that setting is not smooth enough for other channels that I would want to keep it there.

Any idea what they did, what's going on? Seems very strange that an HDTV signal would have such a major variation from other channels.