I have the same issue, CTK 3400SK out of warranty, but mine is the F#3 key. Whenever I press F#3 without releasing it, all neighboring keys from C3 to G3 doesn't seem to sound right. It sounded loud, no matter how soft I pressed these keys. But whenever I release F#3, everything goes back to normal. It sounds annoying playing your keyboard with this issue. I have tried dismantling the entire keyboard, checking, finding what caused it, cleaned and removed the dirt as per advised by the previous forums and youtube videos. I just cant find what caused it. What could probably caused this issue? I just love to have the touch response feature because it helps us express better the music we are playing. Thanks.
