Something perhaps in the way the selenium driver wrapper hangs about means I often have to end-task Pycharm if I am debugging a selenium python project. This happened to me before and after re-installing Windows. Writing this up here in case someone else sees and also has some clues. Pretty sure it's the way I'm using chromedriver and a good few other modules together. It only happens in some of my selenium projects, so will be hard to reproduce.
Does not happen if I just run the app not in debug, but the minute I run in debug, after the debug session ends (the app never exits for some reason), there is thus a zombie process somewhere, and I have to kill Pycharm totally in order to use breakpoints again.