More Awesome Than You!

My entire household seems to be under the misapprehension that they are enjoying a never ending pool party.
Every chance they get they change into swimwear.  If I try to throw a new party I'm told that "you can only be at one party at a time".
I have no idea how this started, because I've never thrown a pool party, ever.
I've tried to move them out and back in, but that causes a CtD.

Why?  Why is it I'm completely unable to play the game beyond a generation or two without the whole neighbourhood going corrupt?  I don't even have CC beyond store crap and some very simple xml-mods.

I've had a seemingly innocent xml mod screw up a game spectacularly before when it went out of date, so don't rule them out.

There hasn't been any updates to cause my XML-mods to go out of date.  And I made most of them myself, so I know exactly what could go wrong.

Anyway, I give up.  I'll take up tetris in stead.

NRaas Overwatch might help with the problem. Use "Cleanup Situations." I don't know if AM has something similar.

Could be borkedness with EA themselves, as I'm having a somewhat similar issue. Any lot with a pool on it, all sims, including NPCs such as the mail carrier and paper deliverer, automatically change into bathing suits and go for the pool all the fucking time. I've put up fences and locked doors to prevent townies and such from freeloading, but my sims refuse to give up the pool/diving board/lounger.

Mine aren't actually using the pool, but they are drawn to the sprinklers (but if I remember correctly AM prevents sims from autonomously playing in sprinklers unless they are in swimwear, so that's normal). 
They change into swimwear and they do so on all lots.  My fire-fighter decided to do his job in a speedo.

I'm giving up.  It looks like the entire game has cone completely corrupt.  NRaas couldn't do anything for it either.

If you haven't already, have you tried reset world?

I've tried resetworld.  I've tried fixall. I've tried resetting every single sim in the household individually.  I've tried without CC.  I've tried moving the family.  I've tried moving the lot.  I've even tried turning my fucking computer off and on again.

Moving the household to a new clean neighbourhood seems to have worked, but I fucking hate doing that.  It takes forever to get things back to the way I like them.

Edit:   The everlasting pool party is gone, but my ultimate sim has gone invisible/stuck underground and none of the usual tricks work.
I suspect that the game just can't handle an immortal sim trying to excel at every skill, job and profession in the game.

It's happening again.
Fucking hell!  >:(