Yamaha DTXpress/DTXplorer/DTXtreme

Hi , i was practicing accented note between hit hat and snare and i 
saw that my accented note on snare pad don't work ( silence ) while i 
hit at the same time hit hat , i first think it's because they are 
too close and maybe vibration cause that but it's the same if i hit 
at the same time any others pad ! , that happen for accented note and 
when i play a little more then acentued , apparently that not happen 
when i play non acentued note , my level gain on snare was 94 , i 
reduce to 64 and problem still the same , anybody had this problem or 
understand what happen ? is it a pad problem or a module problem ? 
thank's for you help 
Stephane