I have had a few crashes while switching from one zone to another, but also a few freezes while not doing anything in particular, just idling. Sorry, nothing I have reproduction steps for.
But this is still an issue even if there are no crashes. If I want to stop playing, I have to close the browser. With no way to manually initiate a save, I will lose progress every time I do this. It used to be up to 1 minute of progress, so not a huge deal. Now it's up to 5 minutes which is pretty annoying.