Yamaha CS80

So I am wondering if this is normal.  I play a few keys on the right side of 
the CS80's keyboard.  The Brilliance is a tad up. I have a long sustain for 
the notes..   Everything is fine..  Sustain is in mode I.

While my right hand is playing melodies.. I then use my left for lower keys. 
  And the sustain from the high notes get cut out once I use the lower notes 
with this setup.  Does anyone know why this is happening?  Also, is this 
normal?  The Brilliance sounds as if it is getting cut off or something..  
hmmm.


Seems to only happen with the keyboard control brilliance is all the way up.