We have a front loading washer & dryer, which has seen its fair share of laundry duty.... Recently, the washer started to have a subtle musty smell to the interior. Following a brief panic that our relatively new machine was on the fritz, I Googled "front loading washer smell" and came up with multiple pages on the topic!
Fortunately, this funky smell problem is common with front loading washers.... Recommended solutions for ridding your machine of this odor include keeping the door open to air out the interior when not in use, wipe down the interior & rubber circular lining for any excess water/debris, and every month or so run your machine with a specific machine washing product. My local grocery carried the brand affresh, a tablet that you place in the machine, and set to a wash cycle, but an alternate product suggested is to use White Vinegar.
I have since tried both methods, and have to say, the Vinegar did the better job.... Pour into the detergent compartment (use the same amount as you would detergent), and run on the hottest cycle. I've done this process twice over the last 2 months, and it completely makes a difference.