My sims' house has got a a roof terrace which they can't vacuum but they feel uncomfortable when spending time up there as the dirty surroundings moodlet comes up.
I have this problem as well ☹️
I can confirm it's not something dirty on the roof, i actually destroyed and rebuilt the entire terrace in an attempt to fix it and the problem came right back.
Check your inventory.
A good tip to get something dirty in an inaccessible place is to hire a scheduled maid Travel to somewhere else before her work schedule starts and return later. you will get a note that a maid cleaned the house and everything dirty has been removed by the game.
It literally only happens on the roof terrace, my sim is fine everywhere else, but when I do "check dust levels" on the roof it says it's dirty.
It's nothing in the inventory, and I'm not gonna hire a maid every week just because of a bug :/
