Game keep crashing, pets disappears and sims get stuck in the cars

The pets my sims get keeps just diapering from the family. So I stopped adding them. I cant use the cars, because when the sims return to the home lot they get stuck on the road, sitting in the air for a lot of game hours. So I stopped using the cars. But now my game just keep crashing at random. It started out just happening once in a while. But it feels like the more I play the more it crashes.