When I exchanged my first KN7 for a Tyros 3 the tempo wheel was also 'slipping' and I did point this out to the Dealer but he told me he wasn't worried as it was a simple job to fix it. Unfortunately, he didn't tell me how but I thought you might like to know that it can be done. Meanwhile, whilst pressing down on the wheel very slightly, I used to turn it slower than usual until it showed the tempo number in the screen. This can then be saved along with your sets to the panel memory.
I can guess how disappointed you feel but give it a try, it might just work for you. If it doesn't, I suggest you email Bill Norrie or Alec Pagida - both highly knowledgeable on the KN7000 and more than likely can tell you what to do about it.
Chin up! Audrey