Okay, I made a mistake and amending a statement I made with the BTD kit, It can accumulate on old saves after 2-3 days on the lot.
After a lot of testing, what I had to do to fix it is this. You have to do it this way or it won't work.
1) While your save file is open, Open Game Options and turn off the dust system in 'bust the dust' tab (if it's on, turn it off)
2) Save and exit the game
3) Re-open the game and play the save
4) After it finishes loading and shows your sims home, open the game options and re-enable BTD's 'dust system'
After a few days, the dust will accumulate again, I tested this across multiple saves of mine, and make sure your robot vacuums are off since they'll clean the floor. (You have to do this for each save that was affected)
(For PC users, This is partly linked to Fogitys unlock if you have the mod. (this mod also causes sims to be promoted in the wrong attire)
If you still run into issues, let me know. I’m still trying to see if it sticks after the dust is vacuumed.**
(edited for clarity)
**edit 2: the dust system does not stick after saving and quitting (after leaving the BTD system on) this is because the game turns it off, despite it looking like it’s on.
it does stick if you leave the lot, come back and turn the system off and on. (Without quitting the game)
If you followed the steps, it will stay for the current gameplay session, if you follow your sim to work or travel, it’ll turn off, so you can reenable it without quitting)
This is a temporary workaround, but it works; the team will need to find out why it’s not remembering the choice.