I have had the KN800, the KN3000, the KN6000, the KN7000, and the KN2600.
I have never had a problem with any of them. I still have the KN800 and the KN2600 and they still work great. I sold the others when Technics pulled the plug on manufacturing any more. I don't like orphans.
I have had many other keyboards also and the only ones that had problems and had to go back to the factory were the Ensoniqs.