Grue.  They should have put lights in the nursery.

I started a new game in Riverview -- legacy style -- that has only one household that has ever been active.  I've played this family up to where the founder is an elder and should go at any time.  The youngest of the 5 children is ready to turn to a teenager at the point that I have the game saved.

Here is the problem:  At some point between 2:30 pm and midnight sim time on the day that this child is set to age to teen, two or more of the sims on the lot become invisible.  If they've been sleeping I can see the hump in the bed, but no head, or hands, or zzzzzz's.  If they are moving about they continue to interact with things -- I can see the refrigerator door open, or the TV come on, but I can't see the sim at all.  Also, there have been a couple of times that one of the sims from the household (which sim seems random) will be teleported from where they might be in the house to the backyard -- about the middle of the lot.  When given other orders they begin to carry them out, but then teleport again back to the backyard.

The game has not crashed.

I've tried resetting the birthday boy, resetting the other invisible sims, changing active households, and restarting the game, without avail.  At some point during the course of the afternoon/evening the invisibility returns.  I've tried aging up the child as soon as he arrives home, and also waiting for him to age on his own -- no difference.  Because of this I've wondered if there might be a problem with Grimmie instead of with the birthday boy.  No evidence either way, really, those things just seem to be the only things out of the ordinary with the day.  I hate to kill off Dad if it isn't a Grim Reaper problem.

This is the first trouble I've had with this family. 

If anyone has any ideas about how I can fix this I would appreciate hearing them.