It rarely happens in my game. It's usually the toddlers and children who are breaking their dollhouses themselves. In my game the bigger problem is that everyone (including adult Sims) seems to be obsessed playing with dolls. Whatever they're doing playing with dolls will always get autonomously queued on them, even when they desperately need to go to the toilet or they're hungry they choose to go play with the dolls.
Placing the dollhouse in another room that's only accessible for toddlers is very helpful suggestion for this obsession too. :)
