A quick update on this, with new information, and a new question:
I did more characterization on the channel that fails (KVUE), and using SiliconDust's diagnostic tool, I noted that the reception interference occurs very predictably and periodically, approximately every 30 seconds.
In
this picture, a "t" in the command window on the left indicates a reception error. Though you cannot obviously discern the time period from the picture, the "t" occurs predictably and periodically, approximately every 30 seconds. Using SiliconDust's graphical tool (the window on the right), when the "t" occurs, the symbol rate drops. The rest of the time, the symbol rate is steady at 100%.
Assuming the diagnostic tool can be trusted, I would expect that the cause of the interference is not due to the physical environment (trees, etc.), unless the TV signal itself has a periodic component that only occurs approximately once every 30 seconds. I tend to think that there is some electronic device emitting an interfering signal on a periodic basis, though I don't know what this could be.
Any ideas?