Hi, I have a 2018 Marco Polo, and my waste water tank is broken. It is not posible to empty it. I opened the drain valve under in botom sheld under the burner, also I didi read that taking out the fuse number 2 helps, i did try that, and have opened the sink at the the same time, nothing. Then I did check the waste water outlet under the car, in the back, and it seems clear. Still no water comes out when the ventil is open. What aslo hapemd is that the displey of the waste water container showed empty, and all of the suden if turned to full. Anybody please have a idea? I am on the trip with the family, and going to a mb dealership will kill us the day, when the solution is maybe easy! Thanks for help