Thank you very much for the bug report. We've been having instances of people struggling to get the game to open on MacOS lately and it seems that "nwjs" not closing properly might be the root cause.
Unfortunately we're not entirely sure WHY it's doing that, since it isn't a program we have any hand in... we're going to do our best to look into it, but for now, we're very grateful you brought this to our attention so we can at least hopefully work on it and warn others.