I don't know your living quarters, but sometimes when that happens and you think there shouldn't be anything happening like that, it's from a hatch in some kind of animal that's died and been left undetected, undiscovered.
maybe a mouse, bird, rat, squirrel or something under the house, in the attic, in the rafters, under the porch/stoop?

yeah that was my first thought too.
but i can't smell or find anything.

they seem to be getting less numerous though.
thank goodness.

thanks for the tip anyway &0)