This has happened a couple times. I will kill the NPC. He will be dead, but... Will keep doing what he was doing. In one instance it was a guy holding his sword and walking in place, even after I looted him. He just kept doing it in his underwear. That one didnt cause me issues but the next one did. After taking out some stormcloak soldier in one of the main quest attacks... He didnt fall. he just kinda stood there.

This was a problem, because he still showed up as a red dot on my radar-dealie. Not only that, but he still showed up as a living NPC to my allies. They kept shooting arrows and trying to stab him, and would not stop.

I was able to stop the madness by console killing him... Which is itself weird since, again, he was already dead and I looted him before using the console. I dont have a question or anything. So long as the console keeps working, It wont be a problem. But its weird enough that it got my attention.

Also I have the unofficial skyrim patch installed, but nothing besides that.