Why is my coffee maker is brewing slowly?
I noticed my filter basket has coffee ground buildup. There are old coffee ground bits built up on my filter basket. Could this be the problem? How do I fix it?
As said above, usually cleaning with a 1:1 mixture of vinegar and water will fix this issue. If the issue still persists after cleaning, you could have an issue with your one-way valve. This valve can become clogged with residues, causing the coffee maker to brew very slowly. Sometimes, you have to replace the valve if it fails completely. Refer to the KF 440 valve replacement/ repair guide.
Here is a link to the Bruan Aromaster KF440 Trubleshooting page, which may answer more of your questions: Braun Aromaster KF 440 Troubleshooting