i dunno if this has only just started happening, or if it's always been there and i've only just come across it
anyway: most of my battles take place on other screens, but occasionally they occur in-place, and when that happens i leave the bodies lying around, just for show
today i noticed that when the player party approaches the dead NPCs then the NPCs go into Idle mode, thus appearing to revive, rather spookily
i originally thought that what was happening was that their Move AI continued to function even after the Battle ended and even though they were dead, because if i added a Block Move AI step to the Battle Start event then it seemed to stop them from "reviving"
however, i've just now seen some NPCs pop up again after battle, even with their Move AI blocked, so i guess the problem may be more subtle