In this latest patch on PC (Steam) when you head to the magic mirror, after you click confirm, the button (as well as the exit button) is no longer active. You need to wait 30-60 seconds for the mirror to unfreeze, but you can scroll through options and all of that. So it's either waiting or reloading to the nearest save. Pretty sure it's a bug. My game isn't modded.
Also, while I'm on that, why does the launcher constantly offers me to buy the DLC update even though I've pre-odered the game & the DLC update was free (included)?