Hi James
Excellent news and Happy New Year to you too!
It looks like the problem that Jenny picked up with the python3 prototype only affects Windows-based Moodle servers. These are fairly rare which is why we haven't seen the issue before.
You should now implement the fix (changing the regex to use \R rather than \n - changing it back again is strictly optional) in the prototype for the python3 question type, which is the question named BUILT_IN_PROTOTYPE_python3 in the System > CR_PROTOTYPES category. You need to be a Moodle admin to do this. Once that's done, python3 questions should work out of the box, without the need to customise each one. The same fix will be needed for the python2, java_method and octave_function question types if you use any of them. I don't think it will be needed for any of the other built-in question types, but please let me know if I'm wrong.
I'll fix the issue for the next release. Many thanks for your patience and help in finding the problem. Fingers crossed that there are no other bugs affecting Windows-based Moodle servers.
Richard