@virushuo Ha, just removed a colorscheme and the cursor shows up. Thanks for you original post triggering me to do these investigation. Moving on now...
@virushuo I felt making the above statement in a rash was a bit unfair, so I created a new user and tried again. This time, vi had a cursor, so it seems the issue is with the original account.
@vnglst Wow, just when I thought a screenshot is not good enough and wanted to take a screen recording. The recording itself (using the Screenshot app on macOS) seemed to have sent some slight disruptions to the balls and the stable state collapsed and they started fighting again.