title_body: How can I lock my coffee filter when it's too hard?
upvoted_answer: You probably have a broken shower (dispersion disc).
  Try removing the shower screen - the metal part that faces the coffee. There's a screw in the center.
  Above the screen is a plastic dispersion disc (shower); it's job is to spread the water across the bed of coffee. Remove it as well - should pry right out, no additional screws.
  It's pretty common for this disc to break - it's made of plastic and is subject to a lot of heat and pressure. Breville sells replacements on their website, you might also get one at ereplacementparts.com [I have no connection to them but I have purchased this part from them].