I've seen that a few times on different enemies, and not just in DAI. Those are usually called "lag monsters" enemies that are dead but, glitched out and sometimes stay standing until you reload, then are either dead or, re spawn, depending on the game.
They happen because, for whatever reason your computer did not process the death of the creature entirely, it lagged out and skipped the crucial bit that would have made the creature die and drop loot. It's stuck and won't interact or react to anything until you reload that area.
Sometimes lowering a setting or two helps with that, sometimes it's just a random glitch in offline games. in MMOs, it's usually high latency.
