I know I'm reviving a very old thread, I think I have a useful information, stuff break if you start the tinker action, then cancel it after some time, also stuff break if you use them when they are dirty, my sim is also level 10 handiness, I was thinking of upgrading the sink and then the carpool arrived, that's when I canceled and the sink was broke, I think it also goes for fires, a fire starts if you cancel the cooking