Malm Question: Smoke when fire is dying out

Acquired this malm wood stove (or fireplace?) off of Facebook marketplace and had it installed by a local and well referenced chimney company. We love it, but when the fire starts to die out, it pushes smoke into the living room and the whole house if we don’t open a window in time. Yes the flu is clean and yes the damper is open! Otherwise, it works incredibly well when the fire is blazing and puts off a perfect amount of heat. Any ideas on what we can do better?

Apologies if this is the wrong place for this question!