All about the Roland Jupiter-series

Hi

I am a new jupiter-6 owner. Problem is that when I in split mode turn 
the "bender" button off the tune of the selected split falls like a 
half note and the two splits arent in tune any more. It happens 
regardless of the vco-1/vco-2 bender buttons are on or off. I 
therefore cant use bend on just one channel. Its either both or none. 
It has nothing to do with master tune, vco tune/range and the vco 
bend. 

Is it normal? If not can where inside can i adjust it?

Regards

Martin