A lot of times, this is caused by the paper filter not sitting in the coffee maker correctly.The easiest way to fix this is to buy a reusable filter. The reusable ones don't ever have issues like this. If you don't want to do this, I was always told to flip the paper filter inside out before installing in which helps it stick to the walls of the basket.

Here is a link to the Bruan Aromaster KF440 Trubleshooting page which may answer more of your questions: Braun Aromaster KF 440 Troubleshooting