I think I've seen this behaviour in the game since before the patch update.
What I think happens is that the house is just on the threshold between clean and dusty. When the maid/butler stars vacuuming up a dustpile, then it tips the floor's dust level to clean, which causes all dust piles and bunnies to vanish instantly. This interrupts the maid vacuuming the pile when it disappears and they kinda do a reset animation.
Then, a second later, the house becomes dusty again because a couple of sim minutes pass and the threshold between clean and dusty is reached again (because they didn't really get a chance to do a full vacuum cycle and push the dust level back enough). New piles and bunnies spawn, and then the maid does the same thing, cleaning a pile, which instantly disappears and they reset.
And then that same thing happens in a forever loop.
When I saw that happening, I built into my vacuum fix mod a workaround for this, where instead of vacuuming a dust pile direct, a maid will go near it and then initiate a full uninterruptible vacuum cycle on a patch of floor instead of an object that will vanish.
