I am using JN with Python 3 and it has started to give me this error with the bran and autochecking:
Notebook changed
The notebook file has changed on disk since the last time we opened saved it. Do you want to overwrite the file on disk with the version open here, or load the version on disk (reload the page)?
It has become a real spam every time you try autochecking (which is every bit if you're working) or saved. Has it happened to someone?
