Hi Oekoeloe,
I'm am not entirely sure if this will help, as I usually have the strays set to 0, using a mod. But there are a couple of things you could try:
Reset Town:
In Edit Town mode - Press Shift-Ctrl-C keys together to bring up cheat console. Type in: resetsim *
Factory Reset
[This is different from a total-game reinstall - This just sets the game back to factory default.]
Move your Sims 3 folder to the desktop or some where safe, and rename it something like Sims 3 Current. Play the game to create a new Sims 3 folder.
Go To: ----> My Documents > Electronic Arts > The Sims 3
If you want to continue to play your previous game-saves, go into the Sims3 folder that you backed up and copy over your game saves, files and such over to the new game to see if that helps.
You may want to read over the following thread for other important files you may want to put back into your game.
How To: Saving folders/files (Sims 3)
http://www.carls-sims-4-guide.com/forum/index.php/topic,16414.msg313134.html#msg313134Doing a factory reset may help with the other (switching Lifetime Wish) as well. Though progress maybe lost, like you mentioned.
Hope this helps and Welcome to the Forum!!
MrsFlynn