I noticed this the other day and other time before but it bugged me a little. I was fighting a dream toad, i hit it with a pug WS and it flipped on its side, which i thought was funny cause i hadn't seen that before. Anyways, it was the quest where it will run away at about 50% to spawn another toad. Well it ran away sliding on its back lol, they also run away when they are stunned. Dunno if anyone else noticed this before, but i think maybe if a monster is stunned it should remain in place until it weres or it dies at least.