Yamaha DTXpress/DTXplorer/DTXtreme

Wow!!

Where did this problem come from??? When playing a constant snare 
beat on the TP65S pad (CENTER), all of a sudden the pad plays up. 
Somehow,
One of the beats produced is LOUDER, or STRONGER than the normal ones.

It sounds terrible!! Seems like there is a "hotspot" within the 
CENTER area of the pad 
that activates or causes this phenomena to occur.

This does not occur on every hit, but randomly as it wishes. 

Any one out there experienced this problem??? What was the fix??

VAP