electronic sticking keys

[joe morocco]

I service a school system and I've been asked to repair some electronic
pianos. They are Yamaha Clivinova CLP 100's. They all share the same problem
of having some sticking and sluggish notes. There are no key bushings on the
keys, only a little return spring like the hammer butt springs found on
Japanese pianos.  Can anyone give me some info????
Joe Morocco RPT
Needham Mass