J.K.
I was told when I bought my new front loader that it's best to run the clean tub cycle and use cleaner tablets at the same time, I have been using "Affresh" tablets, use them once a month. I also wipe the rubber seal, door, and glass, and leave the door open after my laundry is done. I was told it helps to prevent mold and mildew. There is not enough water to cycle through to clean it out each time, so I guess somewhere inside there water and soap residue exists to some point and that is what gets the smell going. I had a problem before that my brand new towels smelled mildewy like I had left them in the washer for a week before drying them. It was awful and I had always put them right in dryer after they washed. Anyway so I was told that is what happens if you don't clean it out regularly and leave the door open.