Miele G692 dishwasher not draining - the inlet/drain light comes on and I find that the area under the silver mesh filter in the base is full of water. When I bail out the excess water and reset the machine it carries on, sometimes until the end of the wash. If I disconnect the waste pipe from the sink and flow it into a bowl, it doesn't happen, which suggests that when there is less head of water it is OK. I have already changed the drain pump (though secondhand). Is there anything else to try apart from putting on a brand new drain pump?