I found how you can trigger the bug!
Product: The Sims 4
Platform: PC
Which language are you playing the game in? Swedish
How often does the bug occur? Every time (100%)
What is your current game version number?1.71.86.1020
What expansions, game packs, and stuff packs do you have installed?
EP: Get to Work, Get Together, City Living, Cats & Dogs, Seasons, Get Famous, Discover University, Eco Lifestyle, Snowy Escape
GP: Outdoor Retreat, Spa Day, Dine Out, Parenthood, Jungle Adventure
SP: Perfect Patio, Cool Kitchen, Spooky, Movie Hangout, Romantic Garden, Kids Room, Backyard, Vintage Glamour, Bowling Night, Fitness, Toddler, Laundry, Moschino, Tiny Living, Nifty Knitting
KITS: Bust The Dust
OTHER: Holiday Celebration
Steps: How can we find the bug ourselves?
1. Start a new save file, create a sim (I created an adult male sim with the traits: Lazy, Slob, Goofy +family ambition)
2. Move into a house, you will immediatle get the Pristine/Clean level (+2 inspired). Wait until your house get the Dusty level (+1 happy).
3. Buy an upright vaccuum cleaner (I bought the cheapest), vacuum once (You will get the Pristine/Clean level).
4. Wait until your home get into Dusty level again (you will get the moodlet, but the bug also occur without the moodlet = you can stop receiving cleanliness moodlets after a while, this is another bug).
5. Cook something on the stove (I tested with grilled cheese and panncakes), the sim will cancel the action to vacuum
What happens when the bug occurs? The sim will start to cook but suddenly cancel their action and start to vacuum instead (leaving the bowl or pan on the stove). Other actions like eating a meal, watching tv/a movie, showering can also get cancelled. The bug only occur on Dusty, Dirty and Filthy level (but you maybe need to use the vaccum cleaner once?). N.B! The bug will not trigger if you have the +2 focused moodlet that you get from vaccuuming. (see 2nd image)
What do you expect to see? The sims completing their action and not cancel it to vacuum
Have you installed any customization with the game, e.g. Custom Content or Mods? No, never used
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. Installed Bust the Dust