Vintage Synth Repair

I have a Korg X5 bought new in 1995 or 6 - after sitting in a closet for a few years, a few of the keys no longer play.  I connected it to a computer, and all of the notes trigger through midi, so the problem is probably in the key contacts.

Does anyone know anything about what kind of contacts are in there?  Know who made the keyboards?  Are they maybe Fatar units with the common double bubble key contacts, or something else?

I can't seem to find a service manual and the owner's manual is no help.

Thanks,
John