Not many, but enough to be annoying. It's clearly the pattern of the holes in my machine drum. This hasn't happened before. So what is it, and what can I do to prevent it happening again? I'm assuming the machine needs some kind of maintenance wash, but I've never done one, & wouldn't know what to do!
You could run a proper machine wash - HG something? - product through, or there's a way of doing it really hot which someone will no doubt come along and be a bit more detailed about! My helpful comment would be to add a towel or couple of old cloths when you do the service wash, an engineer gave me that advice as the cloth sloshing around the machine forces the water around through the holes a bit more. When mine started to do this it turned out to be the beginning of the end though, as it was oil/grime from a bit of the drum that had moved or worn through.
Its likely to be something called the bearings wearing out. I believe they had the drum in place. Have you noticed an increase in noise when the machine is spinning? On some machines they can be replaced relatively cheaply, but not on others and it often means that you will need a new machine.
You could try a couple of tablespoons of soda crystals in the drawer and run the machine on the hottest (95 deg) cycle either empty or with an old towel/small sheet/rag. I did it and it was ok but if the bearings are buggered you need an engineer. The soda crystals are a cheap first step, though.
If they are black mildew and come off when sponged, a service wash and scrubbing the soap drawer and its slot will ckean it.
However I think it is more likely grease from the drum bearings wearing out, will cause permanent staining so stop putting anything nice in it and look for a new machine (unless you have an extended warranty that will cover an expensive repair)