Hi Dan, you are correct on most fronts... since I posted this morning I bit the bullet and upgraded from 10.3 to 10.5, which has indeed fixed my issue.
I was using pycharm, but I then went bare basics by running python.exe, which had the same issue. I narrowed it down to the arcpy module, and it was only on this PC, not my other backup machine, so I thought a repair was in order, and like I said, I did the upgrade instead of a simple repair.
All seems to be working now, but I do thank you for your comments and time in replying to my question.