(mod) Death resets NPC animation, and can't use animations on corpses
1- Death (health set to 0) cancels the current animation and starts a death animation from start ( #1873 related?)
2- Animation functions can't be used on NPC corpses
2: in vanilla PlayGroup and LoopGroup can still be used on NPC corpses, which might be used by mannequins if they have non-idle poses (this one #2513 seems to work only with idle skipanim though).
1: this makes it impossible to give a NPC a scripted death animation without making them stand back up and replay a full death animation when they're actually killed (either by SetHealth 0, or if they're not killed by a script, then by the player possibly hitting the non-dead body).
There is a possible issue with vanilla behaviour: a NPC's death doesn't trigger OnDeath and +1 GetDeadCount if a NPC's death animation can't play or doesn't end. Scripted death animations are possible, but the OnDeath event and "GetDeadCount" can't be used too (because if the NPC's health is set to 0 and then an animation is scripted, the NPC's death won't play; and if an animation is scripted and then the NPC's health is set to 0, it won't play a death animation - unless "PlayGroup idle" is later used)