UPDATE.... My previous post discussed my efforts to rid my rather new front load washing machine of its musty smell. It's been just about 2 months since following the suggestion of switching to Powder Detergent over Liquid Detergent, after reading how the change might make a difference. I should also mention that I have gone a step further and added White Vinegar to every load of laundry (not just reserving it to run through the machine once a month on the Hot Cycle), and I pour it into the cup marked for Fabric Softener. Well, I think my little experiment has paid off, because the odor is gone -- not only from the inside of the machine but from the laundry (particularly towels) too! To be noted, the only issue I have found is that there is not as big of a selection of brands offering HE Powder Detergent as they do HE Liquid. Tide and Gain are the only 2 I have seen and I opted to try/use Tide.
*White Vinegar is performing multiple housekeeping chores.... it is also my go-to Rinse Aid for the dishwasher!