I also tried a KROME 88 and it sounds pretty good, now as far as the dead keys, it would probably be same concept as the Kronos, so maybe someone spilled something inside, or too much dust on the air? for the money the Krome is not bad at all, although I have the KRONOS, I am totally blown away by the sound and the quality is A1.

Being a GC store demo as Nigel stated it probably takes a daily beating resulting in broken keys....I would assume the Kronos has a much better quality key-bed for the money.
All in all the WS/Arr can be very doable for creating music in so many ways..