Whirlpool Duet leaving drum pattern on clothes

Over the past few days I’ve discovered that any white clothes that are washed in my Whirlpool Duet front loader washing machine are coming out with a polka dot pattern that looks very much like the pattern of the drum.

I’ve run my hand over the drum and I don’t feel any residue on the drum.

I’ve cleaned out the filter and did find a sock that was shredded, but subsequent cycles of washes hasn’t turned up any further clothes in the filter.

Whirlpool is no help. They only suggest I call a serviceman, and we all know that cost might exceed the cost of a new washing machine.

Any help would be greatly appreciated.