I think i finally broke it…
after reloading my latest savegame from my RAM Stress test the game welcomed me with 307 (!!!) errors to my face
306 of them being this one
develop-2513 (x64)
radiant/modules/entities.luac:75: unexpected arg "nil" passed to get_player_id()
stack traceback:
[C]: ?
[C]: in function 'error'
radiant/modules/entities.luac:75: in function 'get_player_id'
stonehearth/lib/player/relations.luac:28: in function 'are_players_hostile'
...onehearth/services/server/player/player_service.luac:25: in function 'are_players_hostile'
...h/services/server/population/population_faction.luac:73: in function '_get_threat_level'
...h/services/server/population/population_faction.luac:77: in function '_on_seen_by'
...h/services/server/population/population_faction.luac:70: in function <...h/services/server/population/population_faction.luac:70>
[C]: in function 'push_object_state'
...h/services/server/population/population_faction.luac:70: in function '_monitor_citizen'
...h/services/server/population/population_faction.luac:10: in function 'self'
radiant/modules/events.luac:80: in function <radiant/modules/events.luac:78>
[C]: in function 'xpcall'
radiant/modules/events.luac:78: in function <radiant/modules/events.luac:70>
and the 307th was an old “friend” …the attempt to index local ‘entity’ (a nil value)
well… could be one of these 
