Hi, I have a Casio LK 280 keyboard and some keys squeak. It started about two weeks after I bought it. In the beginning it was only one or two keys, but now a lot of keys squeak when you press them. I also have an old m-audio midi keyboard for almost 8 years and none of its keys make that sound when you press them. Is that usual for Casio keyboards? Is there a solution so that the keys stop making that sound? Thank you.