My KW29 (2019 frame, 2020 model) has the heater in the slide. My problem was reversed. Almost no heat in the bedroom. When the slide is out is was crimping the rear air ducts drastically reducing the air flow. Pull the intake cover and (in mine) the pot and pan drawer below the oven. Reworked the system so the crimp was gone, it took some work and time but solved my problem.
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