The keyboard of my Yamaha NU1 makes a lot of mechanical noise, i.e., clacking caused (as best as I can tell) by the hammers striking the sensors or whatever else takes the place of the strings. Seems to be the sort of noise that something equivalent to a mute bar on an acoustic piano would stop, but there doesn't seem to be a way to insert a felt strip or other thin barrier over those hammers. Noise is uniform from the lowest to the highest note/key, so not a function of uneven wear. Tried resetting, according to owner's manual, to no avail. Would be grateful for suggestions about how to alleviate.