I see what you mean about the ES count, around 6-7pm especially. Very noticeable. Have you figured whether it is caused internally or externally? Or have any correlation to, say, street lights or heating?
For upstream - yes, that will be the UPBO mechanism in action. Right now, you have reduced upstream power (which I guess I expect) but you also have reduced downstream power (which I don't).
Not internally of my own equipment, I suspect its related to my neighbour upstairs, they start using their washing machine and other stuff after 6pm. From what I can see based on tbb graphing data, smokeping and real usage, the errors are not large enough to affect my service so I have left alone at least for now, but I havent done any serious testing tho.
My US ES count is very similar to when I first had this pair live, its averaging barely 1-2 ES a day.