Wednesday night, I found the scheduled Shutdown had been blocked because SD had failed to make its copying procedure. Decided to wait till the next day to check out the cause since CCC had made a copy and TM worked fine all day on another drive.
Thursday forgot about the SD problem, of course. I was then out of town most of the day, so I didn't have much computer time. Last night, with no input/help from me, SD made a successful copy. Haven't checked the logs... if it fixes itself, don't ask for explanations?
"Electrons are slippery things! And they are hard to inspect. Just getting one to be still long enough to take its temperature is difficult. I find it best to just let them do their thing." Albert Edison... or was it Thomas Westinghouse?
Maybe it was Nikola Einstein?