The problem is that the event is first to load when you restart a game. The trash and so on left over from the last time the game was open will be cleared up. However, the game then scatters more trash, weeds, etc, depending on how long the game has been closed. It is this 'later' stuff that isn't cleared up by the maids. If the event appears while the game is open the maids will clear up all the trash.
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To err is human; to arr is pirate.