Smeg 425 Dishwasher - black residue

[mihilli]

We're getting a black gunky residue in our dishwasher. Tried vinegar and a couple of the commercial dishwasher cleaners but it is still happening.

Dishes come out clean.

We're very consicientious about rinsing our dishes before putting them in the dishwasher. We run it on the 55 degree (centigrade) setting normally.

We are using the powerballs as opposed to loose detergent.

Any ideas?

Thanks

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