DIAGNOSIS Biofilm buildup in the moist rubber door boot and detergent dispenser. This is common in front-loaders.
FIX Leave the door and detergent drawer open after every cycle to dry. Monthly: Run a self-clean cycle with washer cleaner or 1/2 cup of bleach on the hottest setting. Wipe the door boot and dispenser with a 10% bleach solution.
IF THAT DIDN'T WORK The drain pump filter area or the rubber bellows under the door boot lip may have trapped debris. Remove the pump filter and clean the cavity. Inspect the inner folds of the boot.
HEADS UP Never use more than the recommended detergent. Residue feeds mold growth. Replace a heavily molded or torn boot (part number DC97-14470A).