DIAGNOSIS The smell isn't coming from the drum you see, it's from the hidden rubber door boot gasket. Mold and gunk build up in its folds, and a standard clean cycle doesn't reach it.
FIX Manually clean the gasket. Pull back every fold and crevice of the rubber door seal and wipe out all the black gunk and debris with a cloth and a mixture of hot water and white vinegar or a washing machine cleaner. Leave the door and detergent drawer open after every wash to let it air dry completely inside.
IF THAT DIDN'T WORK If the smell persists in your clothes, check and clean the drain pump filter. A clogged filter can trap stagnant, smelly water. It's behind the small kickplate panel at the bottom front of the washer.
HEADS UP Using too much liquid detergent or fabric softener is a huge contributor to this problem. It creates a soap scum that mold loves to eat. Stick to the minimum amount of HE detergent, and consider skipping softener altogether.