Is NRaas ErrorTrap not generating any script error reports when this happens? How long has it been since this world has had a MasterController Reset Everything run on it (if ever)? Most of my long-running worlds require one every 6-8 sim weeks or so, perhaps more often for heavily populated worlds like yours is, to keep things running smoothly.
Do you have NRaas GoHere in play? It should help with world lot routing and should also be resetting these sims' routing instructions should they be on their way somewhere already when the game is saved, quit, and then later reloaded; EA standard tends to get confused when this happens and of course most of us are not going to check around an entire world to see if inactive sims are routing to and from places at the moment we wish to stop playing.
