Please don’t feel provoked:
A good solution is: wash your hands before you make music.
(I agree that a different coating would be far better. But we have the product now and it will not change unless it is worthwhile for Elektron to offer an alternative set of keys)
2nd solution: Order a set of new buttons. They don’t cost much. But the postage is incredibly expensive. So it’s better to order more right away.
If necessary, apply a thin coat of varnish to the new keys.
Prevention: Avoid humid, warm air if geographically possible. Do not cover closed - a thin cloth is better than a plastic cover. Do not smoke in the room.