Yamaha DTXpress/DTXplorer/DTXtreme

Sigh, why me?

There doesn't seem to be any complaint on KP65 (Dtxpress II), but now 
it happens to me...

Last night my KP65 suddenly dropouts to very low volume even after I 
turned to the highest volume knob setting at the back, and it also 
had multiple triggers with one kick, sounds like similar problems 
with KP60?

Anybody has open their KP65 to solve this before? I just bought this 
for 3 months, will Yamaha change it for me?

Thanks guys!