After contactng Apple Support and speaking with Amanda who insisted Apple is not aware of any known issue with this, I gave up and called Netflix.
Robert with Netflix was great. I explained what has been going on, directed him to this discussion (and Vandergraff specifically) and after he reviewed it, he reported it to the resource team and then came back to me and asked if I'd be willing to try a couple things. I told him all that I had tried to date (reset, unplug everything, restarting, praying...) and he offered up one more thing - which for the last hour has worked.
With both devices off, unplug the HDMI cable from your ATV and TV, turn the cable around and plug it back in (so the end that was in the ATV is now in your TV and vice versa). I held back from scoffing when he suggested it and I'm grateful I did. So far, it's a fix.
I ran the Example Short movie, now 5800 kbps, res 1920 x 1080, 1:1. 🙂
The HD movie I've been running for more than 45 minutes (which is the longest and most beautiful picture I've had since mid-November) is pure perfection.
Makes me want to skip work today as the temp is frigid in MN, but alas, I've wasted hours on the problem and will keep my fingers crossed that Robert is an angel and prayers do work!
Good luck to all.