This had a surprising answer.  It was the mouse!  ”Turned out to be a really simple fix. A few of the strange behaviors made me think it might have something to do with my mouse. Sure enough, I switched out my mouse and everything is working fine. I guess my old mouse (a 3rd party mouse by Evoluent) went haywire.”  You rarely suspect that kind of problem for this issue.  I was wondering if it might be some kind of damage like a disk or something.