CI555WH marks on laundry.

m/c is two years old. In its first year it caused marks on laundry due to the drum rubbing on the door boot, sending small bits of stickey boot into the washing. Tried the door boot first but ended up replacing the whole tub. Now about one year on I am called back for marks on laundry which will not wash out. Looks like black marks/dots in small areas. Customer says they were stickey but no sign of that now, detergent and dosage were ok but no service wash has been done. Door boot was badly scored by the drum. This seems to be a problem that most of the machines suffer from to a more or lesser extent. I think the heavier the load, the more the drum flex and the more the problem. Changing the tub has not solved the problem so I angle grinded out a groove deeper than the original one, washed the boot and refitted. I asked her to do a service wash and left it with her. Got a call the following day to say it had done the same thing but worse, however she had not done the service wash.
I have now got the machine in the workshop and have done a service wash. Has any one got any comments or advice before I commit my wifes best whites to the test.
Regards,
Mike.