The friend of mine who worked on my PSR2000/2100 keyboards had to replace the contacts. It's from the part wearing out. It's a good sign - that you're having a lot of fun with your keyboard. Of course, contact cleaner - can't hurt trying.

My advice: Get it repaired before you embarrass yourself at a gig. I did a gig where I couldn't use Style Variation D during the second half of the show.

Good luck!

Beakybird