Sorry for the silence on this - it's still on my mind, but I don't know for sure what's wrong since I can't reproduce it. If you can open up the developer tools (right click on the background of the page click Inspect), go to the Console tab and send me whatever is logged there after it fails, that might be helpful. There will probably be a lot of random errors that aren't meaningful, but hopefully at least one that points me to a specific problem.
Short of that, I can work on getting a downloadable Mac build instead of the web version, if that's something you'd be interested in?