It could be caused by sims having water balloon fights, or it is on my computer anyway. It took me a while to figure out what was causing all the pauses in my game, but I noticed a slight lag every time a sim tried to start a water balloon fight and an even bigger lag if I tried to start one myself on a small lot without much space outside. Then get a message saying to clear up some space. Its a pain in the neck when they try to play with a sim thats busy, then they try again with another sim, then another and its pausing every few seconds
The weird thing is my new 5x5 lot lags a lot less than my old smaller lot which makes me think its just the game struggling to find space for the sims to go and play. I stopped going to the Lulu lounge and I dont get bugged by as much lag, my romance sims just have to settle for the Photo Booth at Crypt 'O Night Club instead of the hot tub now. The hot tub warms the sims up and they try to cool off with a water balloon fight...