I just clicked me too. It especially happens when one or two household members spend a day in their restaurant and return home in the evening. The butler comes running towards the house, and it's always three different butlers taking turns. Most often, I see my current butler as a restaurant guest or beach tourist or entertainer in the lounge, while she is supposed to be at home to take care of the toddler. I also don't want my butler on vacation when I leave my kid at home.
I noticed that it happens when one or two sims or the whole household spends a longer time away travelling with the cellphone during the day. It also happens when I spend a day at the beach, but not as often as it happens when I work at the restaurant.
