Yamaha psr-e423 - touch sensitive function doesn't work with some voices

by Zbros
(Malaysia)

Hi, I owned a PSR-E423. Only just recently, I've noticed that the touch sensitive function doesn't work with some of the voices.

The voices that aren't working are:
004 Harpsichord
005 Octave Harpsichord
019-033 (All the organ voices)

Doesn't the touch sensitive suppose to lower the sound if I pressed the key lightly or something? Is this normal?