ive not had this problem with the hag in particular. But i have had this problem when engaging enemies in sneak attacks/ambushes which were supposed to have a cutscene. For me it happened several times with the goblins surrounding the gnome on the windmill. I wanted to ambush them instead of conversing, but as soon as i initiated combat on the named goblin it tried to cut to a cutscene, music came on for battle, and the screen just faded to black.