Hello, my name is Rusty. There are velocity sensitive pads that make sounds when the keys are struck. They can wear out, and are a maintenance item. You can do this at home if you are comfortable removing the cover.
First unplug it. Remove the screws on the bottom of the piano, all of them. The top flips up and exposes the electronics. Now strike any key, and notice where the back of it hits. Those are the contact strips that need to be replaced.
Call(###) ###-#### ***** through Friday, from 7:30AM - 5:00PM Pacific Time (closed 12PM - 1PM) to order new contact strips. Your piano will play like new. Let me know if you have any questions.
What is your zip code? I can put you in touch with a tech.