I tried starting robocopy with doing just one very large folder that has a lot of subfolders. It chugged along fine for a long time, but when I came back and checked later I had a black screen again, along with the not-helpful message "Your computer experienced a problem and had to shut down". Yeah, thanks -- what caused the ◊◊◊◊◊◊◊ problem?
I ran chkdsk on both the source and destination drive -- no issues. I am now working on making a robocopy .bat file to do the folders individually. With all the time I've put into it already, it would have been faster to drag and drop them. But I am a coder, and determined to automate the process so I don't have to do it the long way next time. I'm actually pretty close and will document the solution when I have it.