I just updated over the weekend. And Now I too am seeing that the sort option is set into filename mode by default. This after a router reload as well as boot up.
I will do some investigation. Not sure if this is ticket worthy or not.
As I have my media stored, series especially, in directories based on seasons. So filename is how I usually sort. But if a ticket should be cut. Let me know. I will do so.
Best Regards,
Seth