Sometimes the warning "anim_id isn't set for anchor != location, anchor = being" is written to the logfile. These entries are caused by either GE_HITPOINTS_LOST or GE_HITPOINTS_GAINED game events when the monster dies.
The problem is that once a monster is killed, its data is not provided in the "adom_nelib_draw_map" anymore. So for those events that provide their own "uid" value, we use that instead of the one we could determine in the "adom_nelib_draw_map".