These issues may occur if door seal requires cleaning or it is worn out, as it will rub against the drum and cause these type of issues.
Please try this:
You will have to unplug the appliance and take a dry cloth, wipe inside the door, and clean the door seal.
After the cleaning is done, reconnect everything and plug it back.
Then use 2 washing machine descalers (1 in drawer and 1 in drum) and select an empty wash cycle on its hottest setting.
Please let it complete and then wait for around 1 hour before opening the door.
Now, after one hour unplug it again and then clean the drain pump filter located at the bottom front of appliance and clean the drum and door seal.
If you have ground coffee (you may pour it in a bowl/cup) and leave it for one day inside the drum.
Then next day after all this is done select another empty wash cycle on its hottest setting with washing machine detergent.
Let this complete then, leave it unplugged few hours this time with door open.
The problem should be resolved now and there should not be any black marks on the clothes.
However, if the issue is still there, you will have to replace the door seal.
Alternatively, you may call Zanussi at 03445 610 645 to book repair.
If there is anything else I can help you with, please let me know.