For anyone trying this on another system: you must specifically click on
and drag the mouse/turtle graphic.

Running from IDLE edit, I get no traceback in the Shell Window, unlike
with the script I attached to #7074 and now here. While I am closing the
latter as probably due to the same cause, it does act differently:
adding the 'speed(0)' command present in dragbug.py appears to have
fixed the problem with turtlecrash.py.

Rewriting dragbug to use tkinter canvas directly would determine whether
the turtle module is a factor. The change of behavior with turtlecrash
with the speed command suggests to me that it might be.