Hi guys, I know this is an older post but I have had Error 12 many times and I even lost a legacy because I could not get my game to stop crashing. I finally fixed it and I haven't seen this solution anywhere so I thought I'd share.
My current legacy had the same problem, crashing and Error 12, even after only 10 min of game play, plus it was incredibly laggy. I'm 5th generation in so the neighborhood is very populated but I really didn't want to start over again. I noticed the issue got much worse after returning home from travel. I tried everything, especially because my computer has more than enough memory for the game. I even rewrote the game files to use more memory with no luck.
So I tried to figure out what about travel was making the game such a problem. Meanwhile, in other worlds, my Sims were fine so it didn't seem to be them. Then I realized: after completing adventures, my Sim had thousands of things in their inventory.
Upon returning home to a world where I had a legacy, it just got completely out of hand because I had so many other Sims and things going on.
Then I realized that my Sims had quite the garden and had hundreds of every fruit/vegetable in their inventories too!
I sold all of their relics and things from travel and their fruits, and GUESS WHAT? Hours of game play with no lags, no crashes, and NO ERROR 12!
So for anyone with these errors - those inventories apparently take up too much memory. Clean everything out and it should resolve the problem!
