Hi. I have a Bosch dishwasher that is showing a code E15 and flashing the check water light. The machine was full of water and I have emptied this using a jug. To maximise the amount of water I could empty I removed the filter unit but when I went to replace it the was an obstruction. I then found a white plastic piece loose in the filter chamber. It looks as if there is a piece missing though it may be designed like that. Do you know what this is and what I should do next ?