I have a korg keyboard I've owned for about 12 years and I have a problem with a few of the keys sticking. I had a professional work on it about a year ago and it worked for awhile, but now it's sticking again and I don't want to deal with the expense and the bother of moving this thing. It's nowhere near as large and heavy as a real piano of course, but the thing is still a beast as far as having to move it.

Does anyone have any advice on ways I can unstick the keys without having to take it back to the shop?
J.S. Bach wtc book II prelude 19
Chopin G Minor Ballade No. 1