Black marks appearing on tumble dried clothes?

I have a Zanussi TDS 383 W tumble dryer.
Clothes have begun to get random black marks on them during tumbling. The marks wash off easily.

I have looked into it and it looks like the front of the drum has dropped about 5mm, exposing a gap around the drum seal at the bottom. I think this is a felt seal.

I have not managed to get the back off the dryer yet (need a slim 7mm box spanner which I will 'borrow' from work tomorrow). I don't have any experience of dryers.

How is the front of the drum supported ? I can see a rear bearing but I can't get my head around how the front would be supported ?

Thanks,

Andy