Problem with Yamaha YS100

[Dimensia7]

I'm having a problem that I would like to solve on my YS100.

There is a key that is louder than the others, I'd like to know if I can fix this or if it's a defectuosity. I checked the manual and they don't seem to talk about this.
Does anybody know how to seperately change the volume of each key or at least Reset all the savings and go back to the default parameters?

Thanks a lot everyone!

Mike

 

[Skipp]

yamahas are reset by holding the highest key on the keyboard while booting.

So you press the key on the keyboard (keep it pressed) and turn the power on.

 

[Chrisco]

yamahas are reset by holding the highest key on the keyboard while booting.

So you press the key on the keyboard (keep it pressed) and turn the power on.

Reset to Factory settings => Press highest key while switching on =>
Tried reboot with the power on/off switch as well as plug out and in
=> Doesn't work
So what does?