So this is a real oddity. If I install Python version 3.7.2 into an appstack (version 2.15.0) when I deploy the appstack everything seems fine, but if you go to the Python37\DLLs directory it will immediately crash explorer. I figured out that the files in there that cause the issue are the py.ico, pyc.ico and pyd.ico files. Also, if you install the pylauncher which automatically associates .py files with Python it presumably uses these icon files and then if you browse to a folder with any .py file it will immediately crash explorer. If you change for example py.ico to py.jpg you can then open the folder but if you hover the mouse pointer over the file it will then try to preview the image and...you guessed it crash explorer.
There is clearly a workaround in that I just deleted the .ico files from the appstack and then it doesn't crash explorer but does anyone have any idea why this could possibly even happen?