Thanks for the additional info but it still leaves open questions.  The current versions of python.org installers for macOS (3.8.2 and 3.7.7) and various others over the past couple of years all come with a built-in version of Tk 8.6 and that normally cannot be overriden. So if you are seeing indications that Tk 8.5.x is in use, you are somehow not really using those current versions of python.org installers or you are calling out within them directly to an older version of Tk (via a subprocess call, for example).  The Apple-provided Tk 8.5.x on macOS systems is woefully out-of-date and has known critical bugs, like crashing when typing in composite characters (like option-u then U to produce Ü on an English keyboard).  Anyway, since you have solved the issue for you, I am going to close this issue.