YAMAHA MO6 attack sound

Hello everybody:
My MO6 has a trouble:
Everytime I leave the keyboard a few seconds of no playing, when I play again, the first note played, sounds with a slow attack, that is very notable, in voices like piano, guitar etc.
I already did a factory reset, but the problem persists.
Would anybody please help me to find out if this is an electronic damage or is there any solution via programming.
Thanks a lot.

Out of curiosity, when you use your Mo6 and then play it again, how long has it been on to begin with? Do you have the keyboard on all day long or do you notice this when you first turn it on and is it working properly when you first turn it on. Take note as to about how long it has been on for when the problem begins. It could be a power supply starting to go bad. Let us know