I know they sell dishwasher cleaner here that is sold in Migros and Coop, near the dishwasher tabs, etc. It's often used to remove any build-up of calc / limescale inside the dishwasher, so maybe that would help?

I think each of them are a bit different, but often you unscrew the cap and then put it in the silverware basket, in the machine, upside down and then run it on a high temp. But each bottle will have its own directions.

This is the one I often see sold here, and it says on the label that it's used for removing calc: