Hello everybody! My english isn't that good, so i'm trying to discribe my problem as good as possible

Anyway, the FX depth knob off my korg kp3 doesn't seem to work anymore. When it's fully turn off ( knob turned to the left ) i can still hear the effect. No matter the effect i choose, i could still hear the fx on it's maximum. I'm pretty sure it's no hardware problem.. Anybody an idea? I already tried to do a factory reset and a software update, but the problem still isn't fixed...
Thanks a lot!