Front loaders need to be cleaned regularly. The water and lint can get trapped in the door seal and it can create mould. Even without fabric softner. It is a good idea to wash your machine out with a really hot rinse and bleach or vinegar at least once a month (especially if you only use cold water) and wipe the seal out every couple of weeks, if not every time you wash. This is the only way to stop mould growing in your door seal. Also do not close the door after a wash, make sure you let it air. Fabric softner can wreck a machine especially if you do not use hot water as it needs the hot water to break down.